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PHP : Language Reference : Control Structures : foreach

foreach

PHP 4 introduced a foreach construct, much like Perl and some other languages. This simply gives an easy way to iterate over arrays. foreach works only on arrays, and will issue an error when you try to use it on a variable with a different data type or an uninitialized variable. There are two syntaxes; the second is a minor but useful extension of the first:

foreach (array_expression as $value)
statement
foreach (array_expression as $key => $value)
statement

The first form loops over the array given by array_expression. On each loop, the value of the current element is assigned to $value and the internal array pointer is advanced by one (so on the next loop, you'll be looking at the next element).

The second form does the same thing, except that the current element's key will be assigned to the variable $key on each loop.

As of PHP 5, it is possible to iterate objects too.

Note:

When foreach first starts executing, the internal array pointer is automatically reset to the first element of the array. This means that you do not need to call reset() before a foreach loop.

Note:

Unless the array is referenced, foreach operates on a copy of the specified array and not the array itself. Therefore, the array pointer is not modified as with the each() construct, and changes to the array element returned are not reflected in the original array. However, the internal pointer of the original array is advanced with the processing of the array. Assuming the foreach loop runs to completion, the array's internal pointer will be at the end of the array.

As of PHP 5, you can easily modify array's elements by preceding $value with &. This will assign reference instead of copying the value.

<?php
$arr
= array(1, 2, 3, 4);
foreach (
$arr as &$value) {
$value = $value * 2;
}
// $arr is now array(2, 4, 6, 8)
unset($value); // break the reference with the last element
?>

This is possible only if iterated array can be referenced (i.e. is variable).

Warning:

Reference of a $value and the last array element remain even after the foreach loop. It is recommended to destroy it by unset().

Note:

foreach does not support the ability to suppress error messages using '@'.

You may have noticed that the following are functionally identical:

<?php
$arr
= array("one", "two", "three");
reset($arr);
while (list(,
$value) = each($arr)) {
echo
"Value: $value<br />\n";
}

foreach (
$arr as $value) {
echo
"Value: $value<br />\n";
}
?>

The following are also functionally identical:

<?php
$arr
= array("one", "two", "three");
reset($arr);
while (list(
$key, $value) = each($arr)) {
echo
"Key: $key; Value: $value<br />\n";
}

foreach (
$arr as $key => $value) {
echo
"Key: $key; Value: $value<br />\n";
}
?>

Some more examples to demonstrate usages:

<?php
/* foreach example 1: value only */

$a = array(1, 2, 3, 17);

foreach (
$a as $v) {
echo
"Current value of \$a: $v.\n";
}

/* foreach example 2: value (with key printed for illustration) */

$a = array(1, 2, 3, 17);

$i = 0; /* for illustrative purposes only */

foreach ($a as $v) {
echo
"\$a[$i] => $v.\n";
$i++;
}

/* foreach example 3: key and value */

$a = array(
"one" => 1,
"two" => 2,
"three" => 3,
"seventeen" => 17
);

foreach (
$a as $k => $v) {
echo
"\$a[$k] => $v.\n";
}

/* foreach example 4: multi-dimensional arrays */
$a = array();
$a[0][0] = "a";
$a[0][1] = "b";
$a[1][0] = "y";
$a[1][1] = "z";

foreach (
$a as $v1) {
foreach (
$v1 as $v2) {
echo
"$v2\n";
}
}

/* foreach example 5: dynamic arrays */

foreach (array(1, 2, 3, 4, 5) as $v) {
echo
"$v\n";
}
?>

Related Examples ( Source code ) » control_structures.foreach
















Code Examples / Notes » control_structures.foreach

php

[Ed Note:  You can also use array_keys() so that you don't have to have the $value_copy variable --alindeman at php.net]
I use the following to modify the original values of the array:
<?php
foreach ($array as $key=>$value_copy)
{
    $value =& $array[$key];
    // ...
    $value = 'New Value';
}
?>


oto "zver" brglez ml.

You can use you'r own function for creating xml/html tags.
Function :
function tag($tag,$string,$atrib = false){
if(!is_array($atrib)){
return "<".$tag.">".$string."</".$tag.">";
} else {
$o = "<".$tag;
foreach($atrib as $key => $val){
$o .= " ".$key."=\"".$val."\"";
};
$o .= ">".$string."</".$tag.">";
return $o;
};
}
Usage:
$array[href] = "http://www.php.net";
$array[id] = "testcss";
$array[class] = "simplecssclass";
print(tag("a","PHP Home Page,$array));
Output:
<a href="http://www.php.net" id="testcss" class="simplecssclass">PHP Home Page</a>
You can use this function without attributes. Like this:
print(tag("b",Bold text));
Output:
<b>Bold text</b>


php

With foreach and references, there is a super easy way to corrupt your data
see this test script:
<?php
$array = array(1,2,3);
foreach( $array as &$item );
foreach( $array as $item );
print_r( $array );
?>
You would imagine that it would have 1,2,3 but in reality, it outputs 1,2,2
The issue is that $item is a pointer to the last array value, and exists outside of the scope of the foreach, so the second foreach overwrites the value. If you would check what it gets set to in the second foreach loop, you would see that it gets set to 1 and then 2 and then 2 again.
This has already been filed as a bug, see:
http://bugs.php.net/bug.php?id=29992
but php developers seem to think that it's expected behaviour and *good* behaviour, so it's doubtful that it will change anytime soon. This is a really bad gotcha, so watch out.


timon van overveldt

Why not just do this?
<?php
$arr = array(1, 2, 3, 4);
foreach ($arr as $i => $value) {
  $arr[$i] = $value * 2;
}
// $arr is now array(2, 4, 6, 8)
?>
No need for references, so it works in both PHP4 and PHP5.


tcrosby

Using the much-maligned ability of foreach to work on references rather than copies, it becomes possible to recurse indefinitely into deep arrays without the need to know beforehand how deep they go.  Consider the following example (which I use to sanitize input):
<?php
// Sanitize as a function to allow recursing; original array passed by reference
function sanitize(&$array) {
       foreach ($array as &$data) {
               if (!is_array($data)) { // If it's not an array, clean it
                       $data = '\\' . $data; // addslashes(), mysql_real_escape_string() or whatever you wish to use, this is merely a simple example
               }
               else { // If it IS an array, call the function on it
                       sanitize($data);
               }
       }
}
// Test case
$test = array(
               array(
                       array(
                               0,
                               1,
                               2
                       ),
                       3,
                       4
               ),
               5,
               6
       );
// Output
sanitize($test);
print_r($test);
/*
Output:
Array
(
   [0] => Array
       (
           [0] => Array
               (
                   [0] => \0
                   [1] => \1
                   [2] => \2
               )
           [1] => \3
           [2] => \4
       )
   [1] => \5
   [2] => \6
)
*/
?>
When first called on $test, it passes a reference to the original $test array to the sanitize function, which begins to iterate through its contents with the immediate foreach loop.  Each value that is not in itself an array gets sanitized as normal, and as both the foreach loop and the function itself are acting by reference, all changes happen directly to the contents of the superglobal rather than to copies.  If the value given IS an array, it then calls the same function on it.  The key here is that both the function and the foreach loop work by reference, meaning that you can call the calling function while in the foreach loop and all changes are still applied to the original array, without corruption of the array pointer, as it remains intact for each level of the array.  When the end of an array is reached, the function simply returns; if it was a deeper-level array, the parent function (and parent foreach loop) continue as they were; if the top-level loop ends, then the function returns to the main code, having acted on the entire array.  As everything operates within the scope of the sanitize function, you even avoid the danger of leaving the last reference set, as $data is not available outside the scope of the function in which any particular loop operates.  While this might sound complicated at first, the result is that by passing to foreach by reference, true indefinite recursion is possible.


mikeb

Using PHP5's foreach "as reference" can bite you!
Three guys in my office spent about a day chasing this one's tail, that was causing aberrant behavior in the values of elements of an array.  It turns out to be a consequence of the nature of references, generally.
If you create a reference to a variable, all names for that variable (including the original) BECOME REFERENCES.  To paraphrase "The Highlander," if you want a name to OWN a piece of data, "there can be only one."
To illustrate this point, consider the following code:
<?php
$f = array(
      0 => array('value' => 'three'),
      1 => array('value' => 'three')
    );
foreach ( $f as $k => &$v ) {
 $v['value'] = 'one';
}
$a = $f;
$b = $f;
$b[0]['value'] = 'two';
$b[1]['value'] = 'two';
var_dump($a, $b);
?>
Upon execution, you will find that, although you would expect $a to contain two arrays with 'value' of 'one', $a and $b are identical -- i.e., the changes of []['value'] to 'two' have happened in both arrays.  But, upon further examination of the var_dumps, you will see that both sets' elements [0] and [1] are preceded with "&":  they are references!
The easy solution to this problem turns out to be:  unset the foreach "as-reference" variable ($v) at the bottom of your foreach loop.  This allows the original variable (or array member) to resume ownership of the value and dissolves its "reference-ness".


ldv1970

To the 18-Mar-2005 03:05 post:
See URL: http://bugs.php.net/bug.php?id=30914
The behaviour you describe is incorrect, but the problem might not be with PHP itself.


boxer

To do tables with cells alleatories...
<?
foreach($result as $item)
{
$x++;
if(($x % 2)==0) {
?>
<tr>
 <td align='center' valign='middle' bgcolor='#FFFFFF' width='300'>
<img src="<?=$item['src'];?>" border="<?=$item['border'];?>" alt="<?=$item['alt'];?>">
 </td>
 <td align='center' valign='middle' bgcolor='#FFFFFF' width='300'>
<?=$item['obs'];?>
 </td>
</tr>
<? } else { ?>
<tr>
 <td align='center' valign='middle' bgcolor='#FFFFFF' width='300'>
<?=$item['obs'];?>
 </td>
 <td align='center' valign='middle' bgcolor='#FFFFFF' width='300'>
<img src="<?=$item['src'];?>" border="<?=$item['border'];?>" alt="<?=$item['alt'];?>">
 </td>
</tr>
<?
}
}
?>  
Just it !


edwin_fromutrecht

To comment on the foreach statement behaviour comment below: The reason for this different behaviour is that the foreach statement is equivalent to the each statement. They both make use of an internal pointer. To loop through the complete array after a change you could use the reset statement on the array.

php_man_resp

To atroxodisse:  This behaviour is normal.  PHP arrays are associative arrays but, unlike Perl, with artificial order maintenance.  Keys can be any scalar value except references; of course integers are scalars, so traditional integer-indexed arrays just work.  {You can even have fractions in array indices, as long as you enclose the index in speech marks, such as $array["1.5"]!  This is not unique to PHP, by the way, but existed by accident in some dialects of BASIC seen on 1980s-vintage home computers.}  The foreach loop iterates over keys in chronological order of when they were added to the array, which is *not* necessarily the same as the sort order.  The print_r() function uses the same iteration order.
If you want to add elements to the beginning of an existing numeric array  {or between existing elements -- either using fractional indices, or because you left gaps when populating the array}  and have foreach iterate over them in order, then you will need to use ksort() on the array *first*.


gherson

To "foreach" over the characters of a string, first "preg_split" the string into an array:
<?php
$string="string";
$array = preg_split('//', $string, -1, PREG_SPLIT_NO_EMPTY);
foreach($array as $char) print($char."<br/>");
?>
This outputs:
s
t
r
i
n
g


14-dec-2004 03:29

This is a summary of bug report #26396 having status "wont fix", so the following is not a bug (report), but may need extra highlighting so the novice programmer (like me) can make sense of the second note given above.
Note:  Also note that foreach operates on a copy of the specified array and not the array itself. Therefore, the array pointer is not modified as with the each() construct, and changes to the array element returned are not reflected in the original array. However, the internal pointer of the original array is advanced with the processing of the array. Assuming the foreach loop runs to completion, the array's internal pointer will be at the end of the array.
<?
$myArray = array("a", "b");
foreach($myArray as $anElement) {
 foreach($myArray as $anotherElement) {
   echo $anotherElement;
 }
}
?>
results in "abab", as each foreach works on a copy of $myArray.
However:
<?
$myArray = array("a", "b");
function b() {
 global $myArray;
 
 foreach($myArray as $anotherElement) {
   echo $anotherElement;
 }
}
function a() {
 global $myArray;
 
 foreach($myArray as $anElement) {
   b();
 }
}
a();
?>
results in "ab", ie. both foreach work on the same instance of $myArray because it is referenced as a global variable. Nevertheless, to the casual observer both variants seem equivalent and therefore should produce the same output.


michael t. mcgrew

This can be used to creat a list of urls for a nav bar or links section etc. If you draw the values of array from a mysql database it can be very usefull.
<?php
$arr = array(news, events);
foreach ($arr as $value) {
   echo "<tr><td>Manage <a href=\"./".$value.".php\">".$value."</a></td></tr>";
}
?>
will return
<tr>
<td>Manage <a href="./news.php">news</a>
</td>
</tr>
<tr><td>Manage <a href="./events.php">events</a>
</td>
</tr>


jazfresh

There is a really really big pitfall to watch out for if you are using "foreach" and references.
Recall this example:
<?
$a = "Hello";
$b =& $a;   // $b now refers to "Hello"
$b = "Goodbye"; // BOTH $a and $b now refer to "Goodbye"
?>
This also applies to the loop variable in a foreach construct. This can be a problem if the loop variable has already been defined as a reference to something else.
For example:
<?
// Create some objects and store them in an array
$my_objects = array();
for($a = 0; $a < $num_objects; $a++) {
 $obj =& new MyObject();
 $obj->doSomething();
 $my_objects[] =& $obj;
}
// later on in the same function...
foreach($my_objects as $obj) { // Note that we are trying to re-use $obj as the loop variable
 $obj->doSomethingElse();
}
?>
When the "for" loop exits, $obj is a reference to the last MyObject that was created, which is also the last element in the "my_objects" array.
On every iteration, the foreach loop will do the equivalent of:
<?
$obj = $my_objects[$internal_counter++];
?>
$obj will now refer to the appropriate element in the array.
But recall the reference example at the top. Because $obj was already defined as a reference, any assignment to $obj will overwrite what $obj was referring to. So in other words, on every foreach loop iteration, the last element in the array will be overwritten with the current array element.
To avoid this problem, either use a differently named loop variable, or call "unset()" on the loop variable before you begin the foreach().
It would be more intuitive PHP unset() the loop variable before a foreach began, maybe they'll put that in a later version.


24-jun-2005 11:00

The poster who submitted this loop style for iterating over variables by reference:
<?php
foreach( $object_list as $id => $the_object ) {
 $the_object = &$object_list[$id]; // Re-assign the variable to point to the real object
 // ...
 unset($the_object); // Break the link to the object so that foreach doesn't copy the next one on top of it.
}
?>
Using foreach() means you end up making a copy of the value, and then quickly reassign it to be a reference. This is a waste of the original copy operation.
You may want to consider this, more meaningful and readable alternative:
<?php
reset($object_list);
while (list($key) = each($object_list)) {
  $the_object = & $object_list[$key]; // Re-assign the variable to point to the real object
  // ...
  unset($the_object); // Break the link to the object so that foreach doesn't copy the next one on top of it.
}
?>


juraj5

The place where the manual says that foreach and while constructs using list and each are functionally completely identical is not true.
Consider a block of code where you need to push an additional into an array while it's being iterated. As foreach is running on a copy of the array, it will only iterate through entries that were in the array when foreach was started. The other method will iterate through all entries.
Code demo:
<?php
$array = array('i', 'v', 'a', 'n');
foreach($array as $key=>$value) {
if(implode('', $array) == 'ivan') $array[]='a';
echo $value; } // prints out ivan
array_pop($array);
reset($array);
while (list($key, $value) = each($array)) {
   if(implode('', $array) == 'ivan') $array[]='a';
   echo $value; } // prints out ivana
?>


turadg

The documentation above says "the internal pointer of the original array is advanced with the processing of the array".
In my experience, it's more complicated than that.  Maybe it's a bug in 4.3.2 that I'm using.
If the array variable is created by =& assignment, then it works as described.  You can use current() within the loop to see the next element.
If the array variable is created by an = assignment, the foreach() doesn't advance the pointer.  Instead you must use next() within the loop to peek ahead.
The code below demonstrates.  On my system, the output is the same for both blocks, though one uses next() and the other current().
<?php
$originalArray = array("first", "second", "third", "fourth", "fifth");
print "the array:\n";
print_r($originalArray);
print "\noriginalArray with next():\n";
foreach ($originalArray as $step) {
   $afterThis = next($originalArray);
   print "$step,$afterThis\n";
}
$aliasArray =& $originalArray;
print "\naliasArray with current():\n";
foreach ($aliasArray as $step) {
   $afterThis = current($aliasArray);
   print "$step,$afterThis\n";
}
?>


egingell

That is definitely weird.
Anyway, I found out that if you put something like $ary[] in where either the key and/or the value goes, you'll append all the keys and/or values to that array. Example:
<?php
$array = array(
     'num1' => 'a',
     'num2' => 'b',
     'num3' => 'c'
);
$k = array();
$v = array();
foreach ($array as $k[] => $v[]);
echo '$k => ' . print_r($k, true);
echo '$v => ' . print_r($v, true);
?>
The above code will do this:
$k => Array (
     [0] => num1
     [1] => num2
     [2] => num3
)
$v => Array (
     [0] => a
     [1] => b
     [2] => c
)


robycar

some useful functions for testing boolean values
<?php
$trueValues = array('1', 'true', 't', 'y', 'yes', 'vero', 'v'); //edit with locale values
$falseValues = array('0', 'false', 'f', 'n', 'no', 'falso'); //edit with locale values
function str_to_bool($str) {
 foreach ($GLOBALS['trueValues'] as $value)
 if (strcasecmp($str, $value) == 0)
 return true;
foreach ($GLOBALS['falseValues'] as $value)
 if (strcasecmp($str, $value) == 0)
 return false;
return NULL;
}
function str_is_true($str) {
 return (str_to_bool($str) === true);
}
function str_is_false($str) {
 return str_to_bool($str) === false;
}
/* Test */
str_to_bool('false'); //return false
str_to_bool('vero'); // return true
str_to_bool('php'); //return null
str_is_true('php'); //return false
str_is_false('php'); //return false
?>


xardas@spymac com

Quote:
-------------------------
It makes sense, since you cannot call only keys from an array with foreach().
-------------------------
Why not?
<?php
foreach(array_keys($array) as $string)
{
print 'array key is '.$string;
}
?>


rabiddog

Pretty weird but for future reference
//doesn't multiply the last value
foreach ($ar as &$v){
$v *= 2;
}
foreach($ar as $v){
echo $v. "
";  
}
//works fine
foreach ($ar as &$o){
$o *= 2;
}
foreach($ar as $v){
echo $v. "
";  
}


support

php at kormoc dot com 11-May-2006 10:25 wrote:
With foreach and references, there is a super easy way to corrupt your data.
But you can avoid it by destruction of the hard link $item
<?php
$array = array(1,2,3);
foreach( $array as &$item );
unset($item);
foreach( $array as $item );
print_r( $array );
?>


mike

One great use of foreach is for recursive function calls.  It can handle things that would otherwise need to be hand-coded down to the desired level, which can make for hard-to-follow nesting.
<?
/*
May you never be forced to deal with a structure
like this in real life...
*/
$items = array(
-1,
0,
array(
array(1,2,3,4),
array(5,6,7,8),
array(9,10,11,12)
),
array(
array("a", "b", "c"),
array("d", "e", "f"),
array("g", "h", "i")
)
);

print_array($items, 0);

function print_array($arr, $level)
{
$indent = str_repeat("&nbsp;", $level * 4);

foreach ($arr as $item)
{
if (is_array($item))
{
print $indent . "Item is an array...
\n";
print_array($item, $level + 1);
}
else
print $indent . "Value at current index: " . $item . "
\n";
}
}

?>
This will output:
Value at current index: -1
Value at current index: 0
Item is an array...
   Item is an array...
       Value at current index: 1
       Value at current index: 2
       Value at current index: 3
       Value at current index: 4
   Item is an array...
       Value at current index: 5
       Value at current index: 6
       Value at current index: 7
       Value at current index: 8
   Item is an array...
       Value at current index: 9
       Value at current index: 10
       Value at current index: 11
       Value at current index: 12
Item is an array...
   Item is an array...
       Value at current index: a
       Value at current index: b
       Value at current index: c
   Item is an array...
       Value at current index: d
       Value at current index: e
       Value at current index: f
   Item is an array...
       Value at current index: g
       Value at current index: h
       Value at current index: i
And it could recurse as far as you want it to go.


jagx

On the note of Paul's for loop:
function foo($x) {
  global $arr; // some Array
  for($i=0; $i < count($arr); $i++) {
    if($arr[$i][0] == $x) {
        echo $arr[$i][1]."\n";
        foo($arr[$i][0]);
    }
  }
}
------------
The middle part of the for loop is evaluated every time it loops which means the count function is called as many times as it loops. It's always better (performance/speed wise) to put the count as the initialization code:
function foo($x) {
  global $arr; // some Array
  for($i=count($arr)-1;; $i>=0; $i++) {
    if($arr[$i][0] == $x) {
        echo $arr[$i][1]."\n";
        foo($arr[$i][0]);
    }
  }
}


jonny arnold

Note that you can use the break statement within a foreach loop, should you wish.

ian

Note that foreach is faster than while! If you can replace the following:
<?php
reset($array);
while(list($key, $val) = each($array))
{
 $array[$key] = $val + 1;
}
?>
...with this (although there are functional differences, but for many purposes this replacement will behave the same way)...
<?php
foreach($array as $key => $val)
{
 $array[$key] = $val + 1;
}
?>
You will notice about 30% - 40% speed increase over many iterations. Might be important for those ultra-tight loops :)


flavio from brazil

Like the FOR statement, you can also write:
<?php
foreach($i=1;$i<10;$i++):
  print $i;
endforeach;
?>


flavio tubino from blumenau, brazil

Like the FOR statement, you can also write:
<?php
$a_array=array("a","b","c");
foreach($a_array as $key=>$value):
  print $key." = ".$value."
";
endforeach;
?>


chris

Just as a note - it's generally not enough to just foreach through $_POST or $_GET, then addslashes() (although this often works)... you could be exposing yourself to a bit of nastiness due to magic quotes.
See the discussion example 3 of mysql_real_escape_string, for a bit more info: http://uk.php.net/manual/en/function.mysql-real-escape-string.php


joaohbruni

Iterate through an array of objects, and change property values from original object.
My original code only worked in PHP5:
foreach($array as $element) {
 $element->property = "new_value";
}
Solution for both PHP4 and PHP5:
reset($array);
while (list($key, $value) = each($array)) {
 $element =& $array[$key];
 $element->property = "new_value";
}


18-mar-2005 08:05

It seems that foreach returns different variable types depending on which syntax you use and which version of PHP you are running.
If you use this syntax:
       foreach($array as  $key => $val) {
then the $val variable is a string (or whatever the actual value in the array is).
But if you use this syntax:
       foreach($array as  $val) {
then it appears that the $val variable is an array in PHP 4.3.10, and it is a string (or whatever) in versions 4.3.1, 4.3.2, and 4.3.6 (I haven't tested any other version).


tquick

It is worth noting that the following code works, and has helped me out quite a few times; not to mention saved time.
This may be obvious to some, but it just dawned on me that the following works:
  <?php
 
     foreach($_GET as $x) {
        echo "$x <br />";
     }
  ?>
Lets say we named this file, index.php
We put into the address bar:
/index.php?name=x&page=y&other=z
The code would output:
  x
  y
  z


scarab

It is possible to suppress error messages from foreach, using type casting:
<?
foreach((array)$myarr as $myvar) {
...
}
?>


john factorial

In response to gherson's method of foreach'ing over a string's characters, PHP 5 now provides you with the str_split() function.
So, to foreach through the characters of a string in PHP 5:
<?php
$string="string";
$array = str_split($string);
foreach($array as $char) print($char."<br/>");
?>
This outputs:
s
t
r
i
n
g


pinheirosp

In reply to FatalError, if you use Zend Dev Studio, i'll notice it's report "while(list() = each())" calls as "Using While w/ arrays param". So far, it's may be ambiguous to make things like that.
Prefer to make a clean code and use PHP "kernel" functions to navigate through an array.
Btw, if we take the exec time as example:
//a litte array, just to test =-]
$arr = array();
for($i=0; $i<100000; $i++) $arr[$i] = $i;
//list-each solution
$myTime = microtime(true);
reset($arr);
while (list($key, $value) = each($arr)) {
  $value = ($key * $value);
}
$myTime = microtime(true) - $myTime;
echo("list-each : " . $myTime . "<BR />\n");
//foreach solution
$myTime = microtime(true);
foreach ($arr as $key => $value) {
  $value = ($key * $value);
}
$myTime = microtime(true) - $myTime;
echo("foreach : " . $myTime . "<BR />\n");
/*
output:
list-each : 0.40198588371277
foreach : 0.23317384719849
*/


gpatmore

In reference to the comment by Timon Van Overveldt...
Although your suggestion works for changing the original array, a copy of the original array is still created for nothing.  This may become a performance issue when used with a large array.  
It has been suggested that if your code must be php4 compatible, use the alternative list()...each() style explained above to iterate through an array if you don't need to use a copy.


wout be

If you want to use an array, depending on a variable, you can point to it within a foreach function like this :
$language = EN;
$xyz_EN = array (...);
$xyz_NL = array (...);
foreach ( ${'xyz_'.$language} as ...)
{
 ...
};


janezr

If you want to "look-ahead" values in an associative or non-continuous array, this might help:
<?
$myArray = {'one'=>1,'two'=>2,'five'=>5,'three'=>3}
$all_keys = array_keys($myArray);
foreach ( $all_keys as $key_index => $key ) {
 $value =& $myArray[$key];
 // $all_keys[$key_index+2] gives null if we go past the array boundary - be carefull there
 $value2 =& $myArray[$all_keys[$key_index+2]] ;
 ...
}
?>


endofyourself

If you are trying to do something like:
<?PHP
foreach(
    $someArray1 as $someValue1 ,
    $someArray2 as $someValue2
) {
echo $someValue1;
echo $someValue2;
}
?>
Pleas note that this IS NOT possible (although it would be cool). However, here is another way to acheive a similar effect:
<?PHP
for(
    ;
    list(, $someValue1 ) = each( $someArray1 ) ,
    list(, $someValue2 ) = each( $someArray2 )
    ;
) {
echo $someValue1;
echo $someValue2;
}
?>


elvin

I wrote this code to add each post from a user to every users' txt file. But it only adds the message to the last user in users.txt. The reason of that is...(questmark)
<?php
session_start();
header("Cach-control:private");
$name=$_SESSION['name'];
$nameframe=$name.".txt";
$message=$_POST['message'];
$wierdchars = array("\'", "\"", "\\", ":-)", ":-D", ":-p", ":-(", "=p", ">:0", ":-[", ":-/", ":-\\", ":-X", ":-?", "B-)");
$newchars = array (stripslashes("\'"), stripslashes("\""), "\\", "<img src='smile.gif'>", "<img src='opensmile.gif'>", "<img src='tounge.gif'>", "<img src='sad.gif'>", "<img src='tounge.gif'>", "<img src='yelling.gif'>", "<img src='embarrased.gif'>", "<img src='sosoleft.gif'>", "<img src='sosoright.gif'>", "<img src='quiet.gif'>", "<img src='confused.gif'>", "<img src='cool.gif'>");
$newmessage=str_replace($wierdchars, $newchars, $message);
$fontcolor=$_POST['fontcolor'];
$fontsize=$_POST['fontsize'];
$fontface=$_POST['fontface'];
$users=file("users.txt");
foreach($users as $user)
{
$nameframed=$user.".txt";
$thefile=file_get_contents($nameframed);
$file=fopen($nameframed, "w+");
$body=$name."|".$newmessage."\n";
$body2=$body.$thefile;
$write=fwrite($file,$body2);
fclose($file);
}
echo "<html><head><title>Adding info...</title>";
echo "<script>window.location='frame.php';</script>";
echo "</head>";
echo "<!--Removes ads form page</head><body>";
?>


magistrata

I use this code to do a simple cleanup on information heading from an HTML form into a database:
<?php
 foreach ($_POST as $key => $value) {
   $$key = addslashes(trim($value));
 }
?>


fatalerror

I recommend using a "while" instead of a "foreach," like this:
<?php
while (list($key, $val) = each($array)) {
// Do something...
}
?>
This gives you more control and gets rid of some problems that you may have with the foreach statement.


atroxodisse

I just noticed something.  I created an array, Looped through a mysql result with a while and added values to that array with an index that I incremented manually, starting at position 1.  After closing the while loop I added an element at position 0 of the array.  When I looped through that array with a foreach loop it evaluated the elements starting from the first element that was added instead of starting at position 0.  I'm not sure if that was intentional but it does not seem to be in the documentation.  So in this case looping through the array with a foreach was not the same as looping through it with a for loop like this:
for($i =0; $i<count($myarray); $i++)
To anyone coming from a C or C++ background this might be confusing.


paul chateau

I had the same problem with foreach() and a recursiv function. If you don't want to spend about 1 or 2 hours to solve this problem, just use for() loops instead of foreach().
Some Example:
$arr[] = array(1,"item1");
$arr[] = array(2,"item2");
$arr[] = array(1,"item3");
//$arr[] = ...
//doesn't work
function foo($x) {
  global $arr; // some Array
  foreach($arr as $value) {
     if($value[0] == $x) {
        echo $value[1]."\n";
        foo($value[0]);
     }
  }
}
//just use this
function foo($x) {
  global $arr; // some Array
  for($i=0; $i < count($arr); $i++) {
     if($arr[$i][0] == $x) {
        echo $arr[$i][1]."\n";
        foo($arr[$i][0]);
     }
  }
}
Paul


30-may-2005 06:17

How To Use References In Foreach Safely And Sanely In PHP 4.
There are two really really important points to remember about foreach and references:
1. foreach makes a copy
2. references (and unset!) work by directly manipulating the symbol table
In practice, this means that if you have an array of objects (or arrays) and you need to work on them *in-place* in a foreach loop, you have to do this:
<?php
foreach( $object_list as $id => $the_object ) {
  $the_object = & $object_list[$id]; // Re-assign the variable to point to the real object
  ....
  unset($the_object); // Break the link to the object so that foreach doesn't copy the next one on top of it.
}
?>
This really works. I have used it in dozens of places. Yes, you need it all, including the unset(). You will get extremely hard-to-find bugs if you leave out the unset().
Static.


postmaster

Hey there
Just a note: if you mistakenly write:
foreach($array as $key->$value) {
   ...
}
you're very likely to have the error message "Cannot access empty property". Make sure you use => and not ->
S. Ali Tokmen
http://ali.tokmen.com/


27-jan-2007 06:50

Here is an obvious question to most of the readers, but it took me about two precious minutes to figure out, so I figured I will share it will you:
What will be the output of the following statement:
<?php
$data = array('1' => 'field1', '2' => 'field2');
foreach ($data as $field_index => $field_name);
{
   echo "$field_name";
}
?>
Correct answer is 'field2', and not 'field1field2'. The forgotten semicolon at the foreach line does not trigger a syntax error, but php treats it as an empty statement..
and then the block is run once with the last value set into $field_name.


mark

Here is a solution to an earlier comment I found that worked well for me. It only goes 4 deep on a complex array or object but could go on forever I would imagine.
foreach($_SESSION as $value => $lable1){
echo "The elements of Value1 <B>" . $value . "</B> is <B>" . $lable1 . "</B><br/>\n";
if(is_array($lable1) || is_object($lable1)) {
foreach($lable1 as $value2 => $lable2){
echo "The elements of Value2 <B>" . $value2 . "</B> is <B>" . $lable2 . "</B><br/>\n";
if(is_array($lable2) || is_object($lable2)) {
foreach($lable2 as $value3 => $lable3){
echo "The elements of Value3 <B>" . $value3 . "</B>is <B>" . $lable3 . "</B><br/>\n";
if(is_array($lable3) || is_object($lable3)) {
foreach($lable3 as $value4 => $lable4){
echo "The elements of Value4 <B>" . $value4 . "</Bis <B>" . $lable4 . "</B>><br/>\n";
}
}
}
}
}
echo "
";
}
}


retula

Here is a cool script to optimize all the tables in a database! (mysql only)
<?php
// connect to the db
mysql_connect("host","username","pw");
mysql_select_db("database");
//get all tables
$alletabellen = mysql_query("SHOW TABLES");
//go trough them, save as an array
while($tabel = mysql_fetch_assoc($alletabellen)){
//go through the array ( $db => $tabelnaam )
foreach ($tabel as $db => $tabelnaam) {

//optimize every table
mysql_query("OPTIMIZE TABLE `".$tabelnaam."`") or die(mysql_error());
}
}
?>
Enjoy!


barnacle83-phpnotes

Here are various ways I've seen to iterate arrays by reference in PHP4.
Based on my tests, I have placed them in order of fastest to slowest.
Benchmarking tool I used:
http://phplens.com/phpeverywhere/phpe-2004.htm#a3297
http://phplens.com/lens/dl/JPBS.zip
<?php
// --------------------------------------------------------------------
foreach ( array_keys($myArray) as $key ) {
 $element =& $myArray[$key];
 ...
}
// --------------------------------------------------------------------
foreach( $myArray as $key => $element ) {
 $element =& $myArray[$key];
 ...
 unset($element);
}
// --------------------------------------------------------------------
reset($myArray);
while ( list($key) = each($myArray) ) {
 $element =& $myArray[$key];
 ...
 unset($element);
}
?>
Andrew


hermann

foreach may be used not only to iterate through array elements, but also to iterate through object properties.
Documentation should specify that.


kirk

Foreach by reference bug:
Can anyone explain this one to me? I've had similar problems with the way foreach handles values by reference. This is the simplest example I could come up with:
<?php
$array1 = array('a' => 1);
$array2 = array('b' => 2);
$array3 = array('c' => 3);
$matrix = array($array1, $array2, $array3);
foreach($matrix as &$array)
$array['d'] = 4;
foreach($matrix as $array)
print_r($array);

?>
This should just add the key / value pair ['d'] = 4 to each array.
The expected output is then:
Array ( [a] => 1 [d] => 4 ) Array ( [b] => 2 [d] => 4 ) Array ( [c] => 3 [d] => 4 )
The actual output is:
Array ( [a] => 1 [d] => 4 ) Array ( [b] => 2 [d] => 4 ) Array ( [b] => 2 [d] => 4 )
My guess:
The first foreach loop disrupts the pointer making the second foreach loop point to the last element twice.
Is anyone able to explain this better or create an even simpler example where this happens?


andy

For dual iteration, the internal pointers may need resetting if they've been previously used in a foreach.
<?PHP
for(
    $someArray1.reset(),
    $someArray2.reset();
    list(, $someValue1 ) = each( $someArray1 ) ,
    list(, $someValue2 ) = each( $someArray2 )
    ;
) {
echo $someValue1;
echo $someValue2;
}
?>


daniel dot oconnor

Dangers with References
<?php
$months = array("Jan", "Feb", "March");
foreach ($months as &$month) {
   $month .= "Beep";
}
print_r($months);
foreach ($months as $month) {
   printf("%s\n", $month);
}
?>
Because $month is a reference to $months[2], iterating again with the same varible name causes $months[2] to be overwritten! Oh no!
Ouput:
Array
(
   [0] => JanBeep
   [1] => FebBeep
   [2] => MarchBeep
)
JanBeep
FebBeep
FebBeep


dyer85

Concerning mike's post below, the list and each function style would also work:
<?php

/* Tweak of Mike's original code */

/*
  Additions include Friendly HTML format or normal
  spaces for command line
*/
/*
   May you never be forced to deal with a structure
   like this in real life...
*/
$items = array(
   -1,
   0,
   array(
   array(1,2,3,4),
   array(5,6,7,8),
   array(9,10,11,12)
   ),
   array(
   array("a", "b", "c"),
   array("d", "e", "f"),
   array("g", "h", "i")
   )
);

// HTML formatting
echo "<pre>\n"; print_array($items, 0); echo "</pre>\n";
 
function print_array($arr, $level)
{
$indent='';
// Change to false if you want CLI formatting (no &nbsp; entities)
$html=true;

// Hehe, I've always used 3-spaced tabs
$indent = $html ? str_repeat('&nbsp;', $level * 3) : $indent = str_repeat(' ', $level *3);

// Changed from foreach
while ( list(, $item) = each($arr) )
{      
if (is_array($item))
{
echo $html ? $indent . "Item is an array...
\n" :
$indent . "Item is an array...\n";
print_array($item, $level+1);
}
else
{
echo $html ? $indent . "Value at current index: " . $item . "
\n" :
$indent . "Value at current index: " . $item . "\n";
}
}
}
 
?>


flobee

be aware! take the note in the manual serious: "foreach operates on a copy of the specified array"
when working with complex systems you may get memory problems because of all this copies of arrays.
i love this function (easy to use) and use it more often than "for" or "while" functions but now i have really problems on this and finally found the reason (which can be a mess to find out)!
the sum of memory usage sometimes can be *2 than you really need.


henrik

As stated further up the foreach is consuming a lot of memory if used within large arrays - that is - if the array consists of for instance large objects. I had a case where a foreach caused me to run out of the 256 MB memory that PHP is allowed to handle - but changing to a for() statement completly removed both memory and CPU load.

scott

Apparently the behavior of foreach with classes changed in PHP5. Normally, foreach operates on a copy of the array. If you have something like
<?php
foreach ($array as $value){
   $value = "foo";
}
?>
the original array will not be modified. However, testing this code on PHP5RC1
<?php
class foobar {

var $a;
var $b;

function foobar(){
$this->a = "foo";
$this->b = "bar";
}
}
$a = new foobar;
$b = new foobar;
$c = new foobar;
$arr = array('a' => $a, 'b' => $b, 'c' => $c);
foreach ($arr as $e){
$e->a = 'bah';
$e->b = 'blah';
}
var_dump($arr);
?>
resulted in the following output:
array(3) {
 ["a"]=>
 object(foobar)#1 (2) {
   ["a"]=>
   string(3) "bah"
   ["b"]=>
   string(4) "blah"
 }
 ["b"]=>
 object(foobar)#2 (2) {
   ["a"]=>
   string(3) "bah"
   ["b"]=>
   string(4) "blah"
 }
 ["c"]=>
 object(foobar)#3 (2) {
   ["a"]=>
   string(3) "bah"
   ["b"]=>
   string(4) "blah"
 }
}
It would seem that classes are actually passed by reference in foreach, or at least that methods are called on the original objects.


badbrush

another WARNING about report #26396 having status "wont fix":
Beware of using foreach in recursive functions like...
function sort_folders(&$items, $parent,$level) {
  foreach($items as $item) {
     if($item->parent == $parent) {
         print $item;
         // call recursively...
         sort_folders(&$items, $item, $level+1);
      }
  }
}
         
I struggled a few hours with this code, because I thought the passing the array by reference would be the problem. Infact you can only have ONE foreach for an array at any given time. A foreach inside another foreach does not work.
The manual should definately give some hints about this behaviour.
pixtur


wrm

Another example for printing out arrays.
<?php
$array = array(
1 => 'milk',
2 => 'eggs',
3 => 'bread'
);
foreach ($array as $array => $value) {
          echo "$value<br />";
}
?>


luke

Alright, I had a little error. I had one foreach() declaration, and then another foreach() declaration.
They went:
<?php
//$connections is an array of Socket resources
foreach ($connections as $key => &$value) {
//the code here is impertinent
}
//$users is an associative array
foreach ($users as $key => &$value) {
//the code here is impertinent
}
?>
Alright, now, what error was produced as a result of this?
This one:
"Warning: Cannot use scalar value as array in filename.php on line 69."
I then realized something; the reason for this came from the fact that I used $key, and $value for both of them in the exact same way.
As a response to this, I've developed two ways to fix this:
<?php
//add this to the end of every foreach() you use
unset($key,$value)
?>
OR
Simply use different variables for each one.


thomas dot kaarud

A more elegant way to do this, without involving new arrays or making PHP5-specific code, would be:
<?php
foreach ($a as $x => $a) {
   echo "$b[$x] : $a"; }
?>


tklee1975

A fix in Wordpress.
In the wordpress source "wp-includes/classes.php",
The following may give a warning if "$rewrite" is not an proper associate array.
[Code]
// Look for matches.
$request_match = $request;
foreach ($rewrite as $match => $query) {    
         .............
         ............
}
[/Code]
This is a short-cut solution:
Change  "foreach ($rewrite as $match => $query) {"
to "while (list($match, $query) = @each($rewrite))"
So that the non-array $rewrite warning can be ignored.


dave

A "cheap" way to sort a directory list is like so  (outputs HTML, one indent is 3 non-breaking spaces):
<?php
function echo_Dir($dir, $level) {
//create an empty array to store the directories:
$dirs = array();
//if we were given a directory to list...
if (is_dir($dir)) {
//and if we can open it...
if ($handle = opendir($dir)) {
//change directory:
chdir($dir);
//iterate through the directory
while (false !== ($file = readdir($handle))) {
if ($file != "." && $file != "..") {
if (is_dir($file)) {
//only add legit directories to the array
array_push($dirs,$file);
}//end if
}//end if
}//end while
//sort the array
sort($dirs);
//NOW handle each directory via a foreach loop
foreach ($dirs as $i => $file) {
$to_echo = str_repeat("\t",$level+1) . str_repeat("&nbsp;",$level*3) . $file . "
";
echo $to_echo;
echo_Dir($file,$level+1);
}//end foreach
//return to the parent directory
chdir("../");
}//end if
//close the handle
closedir($handle);
}//end if
}//end function
?>
For an example of what this outputs, check out http://www.davedelong.com/php/echodir.php


steve ward

@ kirk at proofed dot net
If you change the name of the value variable (i.e. $array) in the second foreach loop, the problem goes away.
See explanation here:
"Looping through arrays with foreach"
http://groups.google.com/group/comp.lang.php/msg/bf35784c733ef439


gardan

(PHP 5.0.2)
Pay attention if using the same variable for $value in both referenced and unreferenced loops.
$arr = array(1 => array(1, 2), 2 => array(1, 2), 3 => array(1, 2));
foreach($arr as &$value) { }
foreach(array(1,2,3,4,5) as $value) { }
echo $test[3];
What happens here is that after the first foreach() loop, you have in $value a reference to the last element of $arr (here: array(1, 2)).
Upon entering the second foreach(), php assigns the value. Now value is assigned to where $value (which is still a reference) points, that is, the last element of $arr.
Your output will be "5", not the expected "Array". To be on the safe side, unset($value) before entering the next foreach().


joseph kuan

<?php
Or use array_combine.
$c = array_combine($a, $b)
foreach($c as $aKey => $bVal) {
  echo $aKey;
  echo $bVal;
}
?>


fred

<?
You can easily use FOREACH to show all POST and GET variables from a form submission
function showpost_and_get()
{
 print "<hr><h2>POST</h2>
";
 foreach($_POST as $varName => $value)
 {
   $dv=$value;
    $dv=$value;
    print "Variable: $varName Value: $dv
";
  };
 print "<hr><h2>GET</h2>
";
 foreach($_GET as $varName => $value)
 {
   $dv=$value;
    print "Variable: $varName Value: $dv
";
  };
}


anonymous

"tquick at pixelated dot com", check out `print_r()`.

simplex

"As of PHP 5, you can easily modify array's elements by preceding $value with &. This will assign reference instead of copying the value."
There are cases where array_walk or array_map are inadequate (conditional required) or you're just too lazy to write a function and pass values to it for use with array_map...
My solution to foreach for php 4 and 5 to modify values of an array directly:
<?php
$testarr = array("a" => 1, "b" => 2, "c" => 3, "d" => 4);
$testarr_keys = array_keys($testarr);
$testarr_values = array_values($testarr);
for ($i = 0; $i <= count($testarr) - 1; $i++) {
$testarr[$testarr_keys[$i]] = $testarr_values[$i] * 2;
}
print_r($testarr);
?>


17-sep-2002 05:06

"Also note that foreach operates on a copy of the specified array, not the array itself, therefore the array pointer is not modified as with the each() construct and changes to the array element returned are not reflected in the original array."
In other words, this will work (not too expected):
foreach ($array as $array) {
   // ...
}
While this won't:
while (list(, $array) = each($array)) {
   // ...
}


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if
else
elseif
Alternative syntax for control structures
while
do-while
for
foreach
break
continue
switch
declare
return
require
include
require_once
include_once
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