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PHP : Language Reference : Types : Arrays

Arrays

An array in PHP is actually an ordered map. A map is a type that maps values to keys. This type is optimized in several ways, so you can use it as a real array, or a list (vector), hashtable (which is an implementation of a map), dictionary, collection, stack, queue and probably more. Because you can have another PHP array as a value, you can also quite easily simulate trees.

Explanation of those data structures is beyond the scope of this manual, but you'll find at least one example for each of them. For more information we refer you to external literature about this broad topic.

Syntax

Specifying with array()

An array can be created by the array() language-construct. It takes a certain number of comma-separated key => value pairs.

array( [ key => ] value
, ...
)
// key may be an integer or string
// value may be any value
<?php
$arr
= array("foo" => "bar", 12 => true);

echo
$arr["foo"]; // bar
echo $arr[12]; // 1
?>

A key may be either an integer or a string. If a key is the standard representation of an integer, it will be interpreted as such (i.e. "8" will be interpreted as 8, while "08" will be interpreted as "08"). Floats in key are truncated to integer. There are no different indexed and associative array types in PHP; there is only one array type, which can both contain integer and string indices.

A value can be of any PHP type.

<?php
$arr
= array("somearray" => array(6 => 5, 13 => 9, "a" => 42));

echo
$arr["somearray"][6]; // 5
echo $arr["somearray"][13]; // 9
echo $arr["somearray"]["a"]; // 42
?>

If you do not specify a key for a given value, then the maximum of the integer indices is taken, and the new key will be that maximum value + 1. If you specify a key that already has a value assigned to it, that value will be overwritten.

<?php
// This array is the same as ...
array(5 => 43, 32, 56, "b" => 12);

// ...this array
array(5 => 43, 6 => 32, 7 => 56, "b" => 12);
?>
Warning:

As of PHP 4.3.0, the index generation behaviour described above has changed. Now, if you append to an array in which the current maximum key is negative, then the next key created will be zero (0). Before, the new index would have been set to the largest existing key + 1, the same as positive indices are.

Using TRUE as a key will evaluate to integer 1 as key. Using FALSE as a key will evaluate to integer 0 as key. Using NULL as a key will evaluate to the empty string. Using the empty string as key will create (or overwrite) a key with the empty string and its value; it is not the same as using empty brackets.

You cannot use arrays or objects as keys. Doing so will result in a warning: Illegal offset type.

Creating/modifying with square-bracket syntax

You can also modify an existing array by explicitly setting values in it.

This is done by assigning values to the array while specifying the key in brackets. You can also omit the key, add an empty pair of brackets ("[]") to the variable name in that case.

$arr[key] = value;
$arr[] = value;
// key may be an integer or string
// value may be any value

If $arr doesn't exist yet, it will be created. So this is also an alternative way to specify an array. To change a certain value, just assign a new value to an element specified with its key. If you want to remove a key/value pair, you need to unset() it.

<?php
$arr
= array(5 => 1, 12 => 2);

$arr[] = 56; // This is the same as $arr[13] = 56;
// at this point of the script

$arr["x"] = 42; // This adds a new element to
// the array with key "x"

unset($arr[5]); // This removes the element from the array

unset($arr); // This deletes the whole array
?>
Note:

As mentioned above, if you provide the brackets with no key specified, then the maximum of the existing integer indices is taken, and the new key will be that maximum value + 1 . If no integer indices exist yet, the key will be 0 (zero). If you specify a key that already has a value assigned to it, that value will be overwritten.

Warning:

As of PHP 4.3.0, the index generation behaviour described above has changed. Now, if you append to an array in which the current maximum key is negative, then the next key created will be zero (0). Before, the new index would have been set to the largest existing key + 1, the same as positive indices are.

Note that the maximum integer key used for this need not currently exist in the array. It simply must have existed in the array at some time since the last time the array was re-indexed. The following example illustrates:

<?php
// Create a simple array.
$array = array(1, 2, 3, 4, 5);
print_r($array);

// Now delete every item, but leave the array itself intact:
foreach ($array as $i => $value) {
unset(
$array[$i]);
}
print_r($array);

// Append an item (note that the new key is 5, instead of 0 as you
// might expect).
$array[] = 6;
print_r($array);

// Re-index:
$array = array_values($array);
$array[] = 7;
print_r($array);
?>

The above example will output:

Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
)
Array
(
)
Array
(
[5] => 6
)
Array
(
[0] => 6
[1] => 7
)

Useful functions

There are quite a few useful functions for working with arrays. See the array functions section.

Note:

The unset() function allows unsetting keys of an array. Be aware that the array will NOT be reindexed. If you only use "usual integer indices" (starting from zero, increasing by one), you can achieve the reindex effect by using array_values().

<?php
$a
= array(1 => 'one', 2 => 'two', 3 => 'three');
unset(
$a[2]);
/* will produce an array that would have been defined as
$a = array(1 => 'one', 3 => 'three');
and NOT
$a = array(1 => 'one', 2 =>'three');
*/

$b = array_values($a);
// Now $b is array(0 => 'one', 1 =>'three')
?>

The foreach control structure exists specifically for arrays. It provides an easy way to traverse an array.

Array do's and don'ts

Why is $foo[bar] wrong?

You should always use quotes around a string literal array index. For example, use $foo['bar'] and not $foo[bar]. But why is $foo[bar] wrong? You might have seen the following syntax in old scripts:

<?php
$foo
[bar] = 'enemy';
echo
$foo[bar];
// etc
?>

This is wrong, but it works. Then, why is it wrong? The reason is that this code has an undefined constant (bar) rather than a string ('bar' - notice the quotes), and PHP may in future define constants which, unfortunately for your code, have the same name. It works because PHP automatically converts a bare string (an unquoted string which does not correspond to any known symbol) into a string which contains the bare string. For instance, if there is no defined constant named bar, then PHP will substitute in the string 'bar' and use that.

Note:

This does not mean to always quote the key. You do not want to quote keys which are constants or variables, as this will prevent PHP from interpreting them.

<?php
error_reporting
(E_ALL);
ini_set('display_errors', true);
ini_set('html_errors', false);
// Simple array:
$array = array(1, 2);
$count = count($array);
for (
$i = 0; $i < $count; $i++) {
echo
"\nChecking $i: \n";
echo
"Bad: " . $array['$i'] . "\n";
echo
"Good: " . $array[$i] . "\n";
echo
"Bad: {$array['$i']}\n";
echo
"Good: {$array[$i]}\n";
}
?>

The above example will output:

checking 0:
notice: undefined index: $i in /path/to/script.php on line 9
bad:
good: 1
notice: undefined index: $i in /path/to/script.php on line 11
bad:
good: 1

checking 1:
notice: undefined index: $i in /path/to/script.php on line 9
bad:
good: 2
notice: undefined index: $i in /path/to/script.php on line 11
bad:
good: 2

more examples to demonstrate this fact:

<?php
// Let's show all errors
error_reporting(E_ALL);

$arr = array('fruit' => 'apple', 'veggie' => 'carrot');

// Correct
print $arr['fruit']; // apple
print $arr['veggie']; // carrot

// Incorrect. This works but also throws a PHP error of
// level E_NOTICE because of an undefined constant named fruit
//
// Notice: Use of undefined constant fruit - assumed 'fruit' in...
print $arr[fruit]; // apple

// Let's define a constant to demonstrate what's going on. We
// will assign value 'veggie' to a constant named fruit.
define('fruit', 'veggie');

// Notice the difference now
print $arr['fruit']; // apple
print $arr[fruit]; // carrot

// The following is okay as it's inside a string. Constants are not
// looked for within strings so no E_NOTICE error here
print "Hello $arr[fruit]"; // Hello apple

// With one exception, braces surrounding arrays within strings
// allows constants to be looked for
print "Hello {$arr[fruit]}"; // Hello carrot
print "Hello {$arr['fruit']}"; // Hello apple

// This will not work, results in a parse error such as:
// Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'
// This of course applies to using superglobals in strings as well
print "Hello $arr['fruit']";
print
"Hello $_GET['foo']";

// Concatenation is another option
print "Hello " . $arr['fruit']; // Hello apple
?>

When you turn error_reporting() up to show E_NOTICE level errors (such as setting it to E_ALL) then you will see these errors. By default, error_reporting is turned down to not show them.

As stated in the syntax section, there must be an expression between the square brackets ('[' and ']'). That means that you can write things like this:

<?php
echo $arr[somefunc($bar)];
?>

This is an example of using a function return value as the array index. PHP also knows about constants, as you may have seen the E_* ones before.

<?php
$error_descriptions
[E_ERROR] = "A fatal error has occured";
$error_descriptions[E_WARNING] = "PHP issued a warning";
$error_descriptions[E_NOTICE] = "This is just an informal notice";
?>

Note that E_ERROR is also a valid identifier, just like bar in the first example. But the last example is in fact the same as writing:

<?php
$error_descriptions
[1] = "A fatal error has occured";
$error_descriptions[2] = "PHP issued a warning";
$error_descriptions[8] = "This is just an informal notice";
?>

because E_ERROR equals 1, etc.

As we already explained in the above examples, $foo[bar] still works but is wrong. It works, because bar is due to its syntax expected to be a constant expression. However, in this case no constant with the name bar exists. PHP now assumes that you meant bar literally, as the string "bar", but that you forgot to write the quotes.

So why is it bad then?

At some point in the future, the PHP team might want to add another constant or keyword, or you may introduce another constant into your application, and then you get in trouble. For example, you already cannot use the words empty and default this way, since they are special reserved keywords.

Note:

To reiterate, inside a double-quoted string, it's valid to not surround array indexes with quotes so "$foo[bar]" is valid. See the above examples for details on why as well as the section on variable parsing in strings.

Converting to array

For any of the types: integer, float, string, boolean and resource, if you convert a value to an array, you get an array with one element (with index 0), which is the scalar value you started with.

If you convert an object to an array, you get the properties (member variables) of that object as the array's elements. The keys are the member variable names with a few notable exceptions: private variables have the class name prepended to the variable name; protected variables have a '*' prepended to the variable name. These prepended values have null bytes on either side. This can result in some unexpected behaviour.

<?php

class A {
private
$A; // This will become '\0A\0A'
}

class
B extends A {
private
$A; // This will become '\0B\0A'
public $AA; // This will become 'AA'
}

var_dump((array) new B());
?>

The above will appear to have two keys named 'AA', although one of them is actually named '\0A\0A'.

If you convert a NULL value to an array, you get an empty array.

Comparing

It is possible to compare arrays by array_diff() and by Array operators.

Examples

The array type in PHP is very versatile, so here will be some examples to show you the full power of arrays.

<?php
// this
$a = array( 'color' => 'red',
'taste' => 'sweet',
'shape' => 'round',
'name' => 'apple',
4 // key will be 0
);

// is completely equivalent with
$a['color'] = 'red';
$a['taste'] = 'sweet';
$a['shape'] = 'round';
$a['name'] = 'apple';
$a[] = 4; // key will be 0

$b[] = 'a';
$b[] = 'b';
$b[] = 'c';
// will result in the array array(0 => 'a' , 1 => 'b' , 2 => 'c'),
// or simply array('a', 'b', 'c')
?>

Example2.6.Using array()

<?php
// Array as (property-)map
$map = array( 'version' => 4,
'OS' => 'Linux',
'lang' => 'english',
'short_tags' => true
);

// strictly numerical keys
$array = array( 7,
8,
0,
156,
-
10
);
// this is the same as array(0 => 7, 1 => 8, ...)

$switching = array( 10, // key = 0
5 => 6,
3 => 7,
'a' => 4,
11, // key = 6 (maximum of integer-indices was 5)
'8' => 2, // key = 8 (integer!)
'02' => 77, // key = '02'
0 => 12 // the value 10 will be overwritten by 12
);

// empty array
$empty = array();
?>


Example2.7.Collection

<?php
$colors
= array('red', 'blue', 'green', 'yellow');

foreach (
$colors as $color) {
echo
"Do you like $color?\n";
}

?>

The above example will output:

Do you like red?
Do you like blue?
Do you like green?
Do you like yellow?


Changing values of the array directly is possible since PHP 5 by passing them as reference. Prior versions need workaround:

Example2.8.Collection

<?php
// PHP 5
foreach ($colors as &$color) {
$color = strtoupper($color);
}
unset(
$color); /* ensure that following writes to
$color will not modify the last array element */

// Workaround for older versions
foreach ($colors as $key => $color) {
$colors[$key] = strtoupper($color);
}

print_r($colors);
?>

The above example will output:

Array
(
[0] => RED
[1] => BLUE
[2] => GREEN
[3] => YELLOW
)


This example creates a one-based array.

Example2.9.One-based index

<?php
$firstquarter
= array(1 => 'January', 'February', 'March');
print_r($firstquarter);
?>

The above example will output:

Array
(
[1] => 'January'
[2] => 'February'
[3] => 'March'
)


Example2.10.Filling an array

<?php
// fill an array with all items from a directory
$handle = opendir('.');
while (
false !== ($file = readdir($handle))) {
$files[] = $file;
}
closedir($handle);
?>


Arrays are ordered. You can also change the order using various sorting functions. See the array functions section for more information. You can count the number of items in an array using the count() function.

Example2.11.Sorting an array

<?php
sort
($files);
print_r($files);
?>


Because the value of an array can be anything, it can also be another array. This way you can make recursive and multi-dimensional arrays.

Example2.12.Recursive and multi-dimensional arrays

<?php
$fruits
= array ( "fruits" => array ( "a" => "orange",
"b" => "banana",
"c" => "apple"
),
"numbers" => array ( 1,
2,
3,
4,
5,
6
),
"holes" => array ( "first",
5 => "second",
"third"
)
);

// Some examples to address values in the array above
echo $fruits["holes"][5]; // prints "second"
echo $fruits["fruits"]["a"]; // prints "orange"
unset($fruits["holes"][0]); // remove "first"

// Create a new multi-dimensional array
$juices["apple"]["green"] = "good";
?>


You should be aware that array assignment always involves value copying. It also means that the internal array pointer used by current() and similar functions is reset. You need to use the reference operator to copy an array by reference.

<?php
$arr1
= array(2, 3);
$arr2 = $arr1;
$arr2[] = 4; // $arr2 is changed,
// $arr1 is still array(2, 3)

$arr3 = &$arr1;
$arr3[] = 4; // now $arr1 and $arr3 are the same
?>

Related Examples ( Source code ) » language.types.array



Code Examples / Notes » language.types.array

caifara aaaat im dooaat be

[Editor's note: You can achieve what you're looking for by referencing $single, rather than copying it by value in your foreach statement. See http://php.net/foreach for more details.]
Don't know if this is known or not, but it did eat some of my time and maybe it won't eat your time now...
I tried to add something to a multidimensional array, but that didn't work at first, look at the code below to see what I mean:
<?php
$a1 = array( "a" => 0, "b" => 1 );
$a2 = array( "aa" => 00, "bb" => 11 );
$together = array( $a1, $a2 );
foreach( $together as $single ) {
$single[ "c" ] = 3 ;
}
print_r( $together );
/* nothing changed result is:
Array
(
   [0] => Array
       (
           [a] => 0
           [b] => 1
       )
   [1] => Array
       (
           [aa] => 0
           [bb] => 11
       )
) */
foreach( $together as $key => $value ) {
$together[$key]["c"] = 3 ;
}
print_r( $together );
/* now it works, this prints
Array
(
   [0] => Array
       (
           [a] => 0
           [b] => 1
           [c] => 3
       )
   [1] => Array
       (
           [aa] => 0
           [bb] => 11
           [c] => 3
       )
)
*/
?>


db

[Editor's Note: (Second example.) These are not "arrays in arrays". These are single-dimensional arrays containing stdClass objects; all objects are referenced by default in PHP5. You can see in the var_dump output that they point to the same object.]
Attention with Arrays in Arrays!
If you copy (=) an array which contains arrays it will be REFERENCED not COPIED.
Example:
<?php
/* GOOD ONE */
echo "<b>Here copy (=) works correct:</b>
";
/* Initialise Array 1 */
$x1 = array(array(10,20),array(30,40));
/* COPY Array */
$x2 = $x1;
/* Change some values in Array 2 */
$x2[0][0]=77;
$x2[1][1]=99;
echo "<b>Original:</b><pre>";
var_dump($x1);
echo "</pre><b>Changed Copy:</b><pre>";
var_dump($x2);
/* BAAAAAAAD ONE */
echo "</pre><hr><b>Here copy (=) FAILS:</b>
";
/* Initialise Array 1 */
$a1[0]->bla[0]->id=10;
$a1[0]->bla[1]->id=20;
$a1[1]->bla[0]->id=30;
$a1[1]->bla[1]->id=40;
/* COPY Array */
$a2 = $a1;
/* Change some values in Array 2 (!) */
$a2[0]->bla[0]->id=77;
$a2[1]->bla[1]->id=99;
echo "<b>Original:</b><pre>";
var_dump($a1);
echo "</pre><b>Changed Copy:</b><pre>";
var_dump($a2);
echo "</pre>";
php?>
The output of $a1 and $a2 will be the same..


lars-phpcomments

Used to creating arrays like this in Perl?
@array = ("All", "A".."Z");
Looks like we need the range() function in PHP:
<?php
$array = array_merge(array('All'), range('A', 'Z'));
?>
You don't need to array_merge if it's just one range:
<?php
$array = range('A', 'Z');
?>


mjp

Those with a perl background may be surprised to learn that the 'thick arrow' and comma operators are not synonymous in array construction.
For example, the following are equivalent:
$ary = array("foo" => "bar", 1, 2);
$ary = array("foo" => "bar", 0 => 1, 1 => 2);


25-oct-2006 05:18

This page should include details about how associative arrays are implemened inside PHP; e.g. using hash-maps or b-trees.
This has important implictions on the permance characteristics of associative arrays and how they should be used; e.g. b-tree are slow to insert but handle collisions better than hashmaps.  Hashmaps are faster if there are no collisions, but are slower to retrieve when there are collisions.  These factors have implictions on how associative arrays should be used.


anghuda

this is simpler tha function display_angka_bilangan by ktaufik(at)gmail(dot)com (16-Feb-2005 12:40)
<?
/*
*
* Class : Terbilang
* Spell quantity numbers in Indonesian or Malay Language
*
*
* author: huda m elmatsani
* 21 September 2004
* freeware
*
* example:
* $bilangan = new Terbilang;
* echo $bilangan -> eja(137);
* result: seratus tiga puluh tujuh
*
*
*/
Class Terbilang {
   function terbilang() {
       $this->dasar = array(1=>'satu','dua','tiga','empat','lima','enam',
       'tujuh','delapan','sembilan');
       $this->angka = array(1000000000,1000000,1000,100,10,1);
       $this->satuan = array('milyar','juta','ribu','ratus','puluh','');
   }
   function eja($n) {
   $i=0;
   while($n!=0){
       $count = (int)($n/$this->angka[$i]);
       if($count>=10) $str .= $this->eja($count). " ".$this->satuan[$i]." ";
       else if($count > 0 && $count < 10)
           $str .= $this->dasar[$count] . " ".$this->satuan[$i]." ";
           $n -= $this->angka[$i] * $count;
           $i++;
       }
       $str = preg_replace("/satu puluh (\w+)/i","\\1 belas",$str);
       $str = preg_replace("/satu (ribu|ratus|puluh|belas)/i","se\\1",$str);
       return $str;
   }
}
?>


lesantoso

This Indonesian number speller function is twice
faster(*) than the one provided in class Terbilang by
anghuda(at)gmail(dot)com (25-May-2006 08:52):
http://www.lesantoso.com/terbilang.html
(*) 2.1 vs. 4.2 seconds in processing 10000 random numbers


guillaume beaulieu

There is no warning nor error if you make something like:
foreach($a as $b => $b) {
  print $b;
}
It is somewhat weird, but in the philosophy of "permit everything" of php.


roland dot swingler

Something that tripped me up:
If you mix string and integer keys, be careful if you are doing a comparison on the to find if a string key exists.
For example, this will not do what you expect it to do:
<?php
$exampleArray = array();
$exampleArray['foo'] = 'bar';
$exampleArray[] = 'Will create 0 index';
$keyWeAreLookingFor = "correctKey";
foreach ($exampleArray as $key => $value){
 if ($key == $keyWeAreLookingFor){
   print "Found Key";
 }
}
?>
It will print "Found Key", because (I presume) when PHP makes the comparison between the string "correctKey" and the index 0, it casts the string to an integer, rather than casting 0 to the string "0" and then doing the comparison.
Using === fixes the problem:
<?php
foreach ($exampleArray as $key => $value){
 if ($key === $keyWeAreLookingFor){
   print "Found Key";
 }
}
?>


stochnagara

Regarding the previous comment, thw following code does the job:
<?php
foreach($arr as $key => &$value) {
  $value = 1;
}
?>


jazepstein overat geemail dot com

Regarding the previous comment, the fact that this code has no effect is perfectly expected:
<?php
foreach($arr as $value) {
  $value = 1;
}
?>
The reason that this doesn't work, is because each time that PHP goes through the loop, it _copies_ the value of the array element into $value. So if you assign a new value to the data in $value, it has no effect on the actual array, because you only changed the value of the copy that was put in $value.
As was discovered in the previous post, the only way to get around this problem is to change the value in the original array. Hence, a typical foreach should instead look like this:
<?php
foreach($arr as $key => $value) {
  $arr[$key] = 1;
}
?>


ia

Regarding the previous comment, beware of the fact that reference to the last value of the array remains stored in $value after the foreach:
<?php
foreach ( $arr as $key => &$value )
{
   $value = 1;
}
// without next line you can get bad results...
//unset( $value );
$value = 159;
?>
Now the last element of $arr has the value of '159'. If we remove the comment in the unset() line, everything works as expected ($arr has all values of '1').
Bad results can also appear in nested foreach loops (the same reason as above).
So either unset $value after each foreach or better use the longer form:
<?php
foreach ( $arr as $key => $value )
{
   $arr[ $key ] = 1;
}
?>


petruzanautico

Regarding the message of phoenixbytes:
The line foreach($bad as $baddies); will just yield in $baddies the last value of the array $bad.
I think that wasn't your intention, in that case there are faster and better ways than foreach.
I think what you wanted to do is:
<?php
foreach($bad as $baddies) // make a collection
{
   if (preg_match("/$baddies/i", $mailto)) // find a match
   {
   $addrmail = "false";
   }
   else
   {
   $addrmail = "true";
   }
} // foreach end
?>


mark gukov

Regarding the fact that there's no need to quote arrays keys when enclosed in double quotes: it only applies to single dimensional arrays.
The following works fine:
<?php
$r['a'] = 'apple';
echo "$r[a] is tasty.";
?>
...but in the case of multi-dimensional arrays:
<?php
$r['a']['b'] = 'banana';
echo "$r[a][b] is tasty.";
?>
would result in "Array[c] is tasty."


mu

Recursive arrays and multi-dimensional arrays are the same thing and completely identical.
The following confirms this:
$fruits1["european"]["green"] = "Apple";
$fruits2 = array ( "european"  => array ( "green" => "Apple"));
print ($fruits1 === $fruits2);
Result: 1 (= true)


joe morrison
Programmers new to PHP may find the following surprising:
<?php
$x[1] = 'foo';
$x[0] = 'bar';
echo "Original array:\n";
var_dump($x);
array_pop($x);
echo "Array after popping last element:\n";
var_dump($x);
?>
The surprise is that element 0 is deleted, not element 1. Apparently the notion of "last element" has more to do with how the array is stored internally than with which element has the highest numeric index. I recently translated a Perl program to PHP and was bitten by this one.
My solution was to identify all the places in my code where I could prove that the array elements were assigned sequentially. In those cases it is safe to use array_pop, array_splice, etc. since the array indices correspond with the array layout. For the other cases, my solution was to write replacements for the built-in array functions such as this one:
<?php
function safe_pop(&$a)
{
 if (!isset($a))
   return;
 if (!is_array($a))
   return;
 if (count($a) == 0)
   return;
 unset($a[max(array_keys($a))]);
}
?>


benjcarson

phoenixbytes: The regex you have posted for matching email addresses is incorrect.  Among other things, it does not allow '+' before the '@' (which is perfectly valid and can be quite useful to separate extensions of a single address).  RFC 822 [1] defines the grammar for valid email addresses, and (the extemely long) regex implementing can be found at [2].  Even the "Add Note" page here at php.net says:
[quote]
And if you're posting an example of validating email addresses, please don't bother. Your example is almost certainly wrong for some small subset of cases. See this information from O'Reilly Mastering Regular Expressions book for the gory details.
[/quote]
A note to others: please do your homework before writing another email-matching regex.
[1] http://www.ietf.org/rfc/rfc0822.txt?number=822
[2] http://www.ex-parrot.com/~pdw/Mail-RFC822-Address.html.


crozzer

Passing variables into the array constructor:
Just a NOOB pointer, I couldn't find other examples for this.  If you want to pass the value of an existing variable into the array() constructor, you can quote it or not, both methods are valid.
<?
$foo_value = 'foo string';
$bar_value = 'bar string';
$myArray = array(
   'foo_key' => $foo_value,     // not quoted
   'bar_key' => "$bar_value");   // quoted
foreach ($myArray as $k => $v) {
  echo "\$myArray[$k] => $v.<br />\n";
}
?>
Both of these will work as expected, but the unqoted $foo_value method above is marginally faster because adding quotes adds an additional string de-reference.


spudley

On array recursion...
Given the following code:
<?
$myarray = array('test',123);
$myarray[] = &$myarray;
print_r($myarray);
?>
The print_r() will display *RECURSION* when it gets to the third element of the array.
There doesn't appear to be any other way to scan an array for recursive references, so if you need to check for them, you'll have to use print_r() with its second parameter to capture the output and look for the word *RECURSION*.
It's not an elegant solution, but it's the only one I've found, so I hope it helps someone.


mortoray

On array copying a deep copy is done of elements except those elements which are references, in which case the reference is maintained.  This is a very important thing to understand if you intend on mixing references and recursive arrays.
By Example:
   $a = array( 1 );
   $aref_a = array( &$a );
   $copy_aref_a = $aref_a;
   $acopy_a = array( $a );
   $copy_acopy_a = $acopy_a;
   $a[] = 5;
   $acopy_a[0][] = 6;
   print_r( $aref_a ); //Shows: ( (1,5) )
   print_r( $copy_aref_a ); //Shows: ( (1,5) )
   print_r( $acopy_a ); //Shows: ( (1, 6) )
   print_r( $copy_acopy_a ); //Shows: ( (1) )


cameron brown

Negative and positive array indices have different behavior when it comes to string<->int conversion.  1 and "1" are treated as identical indices, -1 and "-1" are not.  So:
$arr["1"] and $arr[1] refer to the same element.
$arr["-1"] and $arr[-1] refer to different elements.
The following code:
<?
 $arr[1]    = "blue";
 $arr["1"]  = "red";
 $arr[-1]   = "blue";
 $arr["-1"] = "red";
 var_dump($arr);
?>
produces the output:
array(3) {
 [1]=>
 string(3) "red"
 [-1]=>
 string(4) "blue"
 ["-1"]=>
 string(3) "red"
}
This code should create an array with either two or four elements.  Which one should be the "correct" behavior is an exercise left to the reader....


carl

Its worth noting that there does not appear to be any functional limitations on the length or content of string indexes. The string indexes for your arrays can contain any characters, including new line characters, and can be of any length:
<?php
$key = "XXXXX";
$test = array($key => "test5");
for ($x = 0; $x < 500; $x++) {
 $key .= "X";
 $value = "test" . strlen($key);
 $test[$key] = $value;
}
echo "<pre>";
print_r($test);
echo "</pre>";
?>
Keep in mind that using extremely long array indexes is not a good practice and could cost you lots of extra CPU time. However, if you have to use a long string as an array index you won't have to worry about the length or content.


don dot hosek

It's slightly faster to use array_splice to remove an element of an array:
array_splice($array, $index, 1)
than to do it using the suggested method of unset and reindex:
unset($array[$index]);
$array = array_values($array);
The difference, however, is very small. With 950 iterations I had times of
unset and reindex: 0.22837495803833
splice: 0.22392416000366


akamai

It is quite simple, but don't forget when you'll using foreach with forms arrays.
If your field name is:
<input type="checkbox" name="foo['bar'][]" ...
It doesn't work.
This should work:
<input type="checkbox" name="foo[bar][]" ...


uzakufuklar

It is a kind of simple muti-dimensional array list.
I have made it just to give a simple idea.
<?php
echo "Here we'll see how to create a multi-dimensional array.\n";
$a=array('fruits'=>array('a'=>'orange',
                     'b'=>'grape',c=>'apple'),
'numbers'=>array(1,2,3,4,5,6),
'holes'=>array('first',5=>'second',
                                                         'third')
);
foreach($a as $list=>$things){
foreach($things as $newlist=>$counter){
echo $counter;
}
}
?>


php dot net

in response to ch dot martin at gmail dot com
If you are using the following code:
<?php
$r = array('05' => "abc", '35' => "def");
foreach ($r as $key=>$value)
  var_dump($key);
?>
and you need the array key '35' to be a string (for looping maybe), you can make sure the key is a string by appending a 0 on the front.
'035' instead of '35'


sales

if you need to check a multidimensonal array for values it's handy to store it like
$ar['key1'][0]
$ar['key2'][0]
$ar['key3'][0]
$ar['key1'][1]
$ar['key2'][1]
$ar['key3'][1]
and to loop the keys.
Fill the array (from a database-request):
while($rf=mysql_fetch_row($rs))
{
$nr=$rf[0];
$channel['nr'][$nr]=$rf[1];
$channel['chatter'][$nr]=$rf[2];
}
Call the values:
foreach(array_keys($channel['nr']) as $test)
{
print ' nr:'.$test.'
';
print 'value nr: '.$channel['nr'][$test].'
';
print ' chatter: '.$channel['chatter'][$test].'
';
}
This is useful, if you have to look later for an element
inside the array:
if(in_array($new_value,$channel['nr'])) print 'do something.';
Hope this helps someone.


agape_logos

I was having trouble getting javascript arrays and php arrays to work together with a Check All checkboxe.  Here is a simple solution.  Clicking the 'Check All' checkbox will check all checkboxes on the form.
<script language="JavaScript">
function chkAll(frm, arr, mark) {
 for (i = 0; i <= frm.elements.length; i++) {
   try{
     if(frm.elements[i].name == arr) {
       frm.elements[i].checked = mark;
     }
   } catch(er) {}
 }
}
</script>
<form name='foo'>
<input type="checkbox" name="ca" value="1" onClick="chkAll(this.form, 'formVar[chkValue][]', this.checked)">
<?php
for($i = 0; $i < 5; $i++){
echo("<input type='checkbox' name='formVar[chkValue][]' value='$i'>");
}
?>
</form>
Dean M.


phoenixbytes

i use the array() function for deciding upon an email address's validity, i have a 'wap stalker' of my site that loves to exploit every hole i leave, so i used the following script to avoid being email bombed with my own file sender script, the array() is used to filter out undesirable email providers and, of course, any and all of my own addresses. before all that i used a REGEX to make sure it's an actual email address before going any further.
$mailto = "mail.domain.org"; // the input to be tested
if (preg_match("/^[A-Z0-9._%-]+@[A-Z0-9._%-]+\.[A-Z]{2,6}$/i", $mailto)) // see if it's really an email address
{
$bad = array('mytrashmail.com', 'mymail.ro', 'acasa.ro', 'gala.net', 'phoenixbytes'); // pick out the victims
foreach($bad as $baddies); // make a collection
if (preg_match("/$baddies/i", $mailto)) // find a match
{
$addrmail = "false";
}
else
{
$addrmail = "true";
}
}
else
{
$addrmail = "false";
}
$addrmail can then be used in an argument.
$baddies can be used to give a list, if necessary.
i hope this helps someone.


chroniton .at. gmx .dot. li

I didn't find this anywhere in the docs and i think it is worth a mention:
$a[] = &$a;
print_r($a);
// will output:
/*
Array
(
   [0] => Array
*RECURSION*
)
*/
// this means that $a[0] is a reference to $a ( that is detected by print_r() ). I guess this is what the manual calls 'recursive arrays'.


olegk, getmequick

Hey..
here is a function which helps to avoid using empty/isset
checkings for arrays.
(it's acts simillar to 'default' modifier in Smarty)
Using this function you will avoid 'Undefined index' or
'Undefined offset' error.
<?php
$_POST['id']['other'] = 'val1';
/*
key exist (same as $_POST['id'][other])
*/
echo getRequestParam('id[other]', 'default value');
/*
key doesn't exist, we get default value (same as $_POST['var'])
*/
echo getRequestParam('var', 'default value');
function getRequestParam( $var, $default = '', $method = 'post' )
{
preg_match_all('!(\w+)!i',$var, $match );
array_shift($match);
$_vars = $match[0];
$ret = null;

if( strtoupper($method)   ==  'POST' ) {
$ret = _findRequestParam($_vars, $_POST);
}
elseif( strtoupper($method) == 'GET' ) {
$ret = _findRequestParam($_vars, $_GET);
}
elseif( strtoupper($method) == 'COOKIE' ) {
$ret = _findRequestParam($_vars, $_COOKIE);

}
elseif( strtoupper($method) == 'SESSION' ) {
$ret = _findRequestParam($_vars, $_SESSION);
}

if (! $ret )
      return $default;
else
return $ret;    

}
/**
@access private
*/
function _findRequestParam($vars, $find_in , $curr_key = 0)
{
static $ret;

if( array_key_exists($vars[$curr_key], $find_in) ) {
if( count( $vars)-1 == $curr_key ) {
$ret =  $find_in[$vars[$curr_key]];
}
elseif( $curr_key < count( $vars)-1 ) {
_findRequestParam( $vars, $find_in[$vars[$curr_key]], $curr_key+1  );
}
}
return $ret;
}
?>
Hope this will help someone!


z

Here's a simple function to insert a value into some position in an array
<?php
function array_insert($array,$pos,$val)
{
$array2 = array_splice($array,$pos);
$array[] = $val;
$array = array_merge($array,$array2);

return $array;
}
?>
and now for example...
<?php
$a = array("John","Paul","Peter");
$a = array_insert($a,1,"Mike");
?>
Now $a will be "John","Mike","Paul","Peter"


ktaufik

For you who works for localized "say" number to letter ( ex , 7=> seven, 8=>eight) for Bahasa Indonesia.
Indonesia "say" or "Terbilang" is based on 3 digit number.
thousands, millions and trillions .... will be based on the 3 digit number.
In Indonesia you say 137 as "Seratus Tiga Puluh Tujuh"
<?php
//build random 3 digit number to be "said" in Bahasa Indonesia
$x=rand(0,9);
$y=rand(0,9);
$z=rand(0,9);
function display_angka_bilangan($n) {
  $angka = array(
    1 => 'satu',
    2 => 'dua',
    3 => 'tiga',
    4 => 'empat',
    5 => "lima",
    6 => 'enam',
    7 => 'tujuh',
    8 => 'delapan',
    9 => 'sembilan'
  );
  return $angka[$n];
}
// Terbilang X-------Say X
if ($x==1){$terbilangx="seratus ";}
elseif ($x==0){$terbilangx='';}
else {$terbilangx=''.display_angka_bilangan($x).' '.'ratus ';}
// Terbilang Y ------Say Y
if ($y==0){$terbilangy='';}
elseif ($y==1 && $z==1){$terbilangy="sebelas";$terbilangz='';}
elseif ($y==1 && $z==0){$terbilangy="sepuluh ";$terbilangz='';}
elseif ($y==1 && $z!==1 &&  $z!==0){$terbilangy=''.display_angka_bilangan($z).' belas ';}
else {$terbilangy=''.display_angka_bilangan($y).' '.'puluh ';}
// Terbilang z ------Say z
if ($z==0){$terbilangz="";}
elseif ($z==0 && $y==1){$terbilangz="";}
elseif ($z==1 && $y==1){$terbilangz="";}
elseif($y==0) {$terbilangz="".display_angka_bilangan($z);}
elseif ($y==1 && $z!==1 &&  $z!==0) {$terbilangz="";}
else {$terbilangz="".display_angka_bilangan($z);};
$terbilang=$terbilangx.$terbilangy.$terbilangz;
echo $x.$y.$z." ";
echo $terbilang;
?>
Hope it is useful
ktaufik(at)gmail(dot)com


philip

For all of you having problems when using php arrays in an HTML form input field name, and wanting to validate the form using javascript for example, it is much easier to specify an id for the field as well, and use this id for validation.
Example:
<input type="text" id="lastname" name="fields[lastname]">
then in the javascript check:
if(formname.lastname.value == "") {
    alert("please enter a lastname!");
}
This works very well. If you have any problems with it, let me know.


sezer yalcin - pcdscorp.com

For advanced PHP users:
Here is what happens to keys when you use $a[] syntax:
$a[] = 1; // key is 0
$a[] = 1; // key is 1
So it goes from 0 to 2147483647
Then jumps to -2147483648 and goes up to 0 again.
(if you do $a[] for 4294967296 times)
When its 0, it starts over and does 0, 1, 2 ...
I needed to investigate this in order to avoid any instability. Our spam filter MAHAN does this $a[] millions of times but removes completed elements so that there is no memory outage.


ch dot martin

Extremely irritating quirk regarding the variable types of array keys:
<?php
$r = array('05' => "abc", '35' => "def");
foreach ($r as $key=>$value)
var_dump($key);
?>
The first var_dump for '05' is:
string(2) "05"
as expected.  But the second, '35', turns out as:
int(35)
Php apparently decided to make the 35 became an int, but not the 05 (presumably because it leads with a zero).  As far as I can see, there is absolutely no way of making string(2) "35" an array key.


wmoranatpotentialtechdotcom

Dereferencing arrays takes some time, but is not terribly expensive.
I wrote two dummy loops to test performance:
for ($i =0; $i < count($a); $i++) {
$x = $a[$b[$i]];
$y = $a[$b[$i]];
$z = $a[$b[$i]];
}
for ($i =0; $i < count($a); $i++) {
$q = $b[$i];
$x = $a[$q];
$y = $a[$q];
$z = $a[$q];
}
The first loop is 6.5% slower than the second.  Meaning that dereferencing arrays is not terribly expensive, unless you do it a whole lot. I would expect that each extra reference costs about 3% in speed. The lesson is that if you're going to be using a specific value in an array for a number of operations, you can gain a little speed by assigning it to a temp variable (or creating a reference with $q = &$b[$i]) but it's not worth getting crazy over.
I tested this with iterations of 10,000 and 100,000 on php 4.2 and the results were consistent.


jeff splat codedread splot com

Beware that if you're using strings as indices in the $_POST array, that periods are transformed into underscores:
<html>
<body>
<?php
   printf("POST: "); print_r($_POST); printf("<br/>");
?>
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
   <input type="hidden" name="Windows3.1" value="Sux">
   <input type="submit" value="Click" />
</form>
</body>
</html>
Once you click on the button, the page displays the following:
POST: Array ( [Windows3_1] => Sux )


hramrach_l

Arrays can be merged using + as discussed in the notes for array_merge.
http://www.php.net/manual/en/function.array-merge.php


conorj

Another note on unquoted array indices. Because it is first interpreted as a constant, it must obey the naming convention of constants. i.e. a letter or underscore followed by optional letter, digit and/or underscore characters.
Therefore while the following array declaration is legal:
$a = array('1st'=>'First','2nd'=>'Second');
Trying to access either array item as follows causes an error:
$first = "$a[1st]";
$second = "$a[2nd]";


kal

About the automatic conversion of bare strings...
My opinion is that it never should have been implemented. Isn't it easier to NOT implement this "handy" feature in the first place? It is such a convenient way for "smart" programmers to write unsafe, not-futureproof code. Please remove this feature from future versions of PHP, please. (Hey, if you could change the OOP mechanisms between PHP 4 and PHP 5, why can't you make this change, right?)


moehbass

<b>Mark Gukov</b> wrote below:
Regarding the fact that there's no need to quote arrays keys when enclosed in double quotes: it only applies to single dimensional arrays.
The following works fine:
<?php
$r['a'] = 'apple';
echo "$r[a] is tasty.";
?>
...but in the case of multi-dimensional arrays:
<?php
$r['a']['b'] = 'banana';
echo "$r[a][b] is tasty.";
?>
would result in "Array[c] is tasty."
-----------------------------------------------------------------
However, the following runs fine;
$r['a']['b'] = 'banana';
echo "{$r[a][b]} is tasty.";
Just box it!


sid trivedi

<?php
//Simple Login Script using associative array.
//You may modify the codes and use $_POST['FORM_FIELD_DATA'] for your web-page.
//You may spice-up the codes with more form field validation & security features.
//$user_name=$_POST['user_name'];
//$password=$_POST['password'];
$test_user_name = 'michelle_smith'; //for testing purpose only
$test_password = 'msmith321'; //for testing purpose only
$user_name = $test_user_name;
$password = $test_password;
// here user_name is key and password is the value of an array..
// website owner has to add new user/site member manually in $login_array
$login_array = array(
'user_name' => 'password',
'alex_duff' => 'alx321',
    'xena78' => 'xena321',
'dela_pena' => 'delp321',
'shawn_1981' => 'shw81',
'michelle_smith' => 'msmith321');
ksort ($login_array);
reset($login_array);
if (isset($login_array[$user_name]))
{
$pass_check = $login_array[$user_name];
if ($password === $pass_check)
{
echo  "Welcome, $user_name!\n
"; //may redirect to specific webpage.
}
else
{
echo "Please try again!"; //may redirect to Error page.
}
}
else
{
echo "Please register with us. Thanks!"; //may redirect to registration page.
exit();

}
echo("\n
");
echo 'Thanks to Thies C. Arntzen, Stig Bakken, Shane Caraveo, Andi Gutmans, Rasmus Lerdorf, Sam Ruby, Sascha Schumann, Zeev Suraski, Jim Winstead, Andrei Zmievski for wonderful PHP!';
?>


gautam

<?php
//EXAMPLE  of Multi-Dimentional Array where as an array's keys are an array itself.
//It's so easy to create one like this.
$movie_to_watch = array ('Action'=>
 array('Kanu Reeves' => 'Matrix Reloaded',
                     'Pearce Brosnan' => 'Die Another Day',
                     'Tom Cruz' => 'Mission Impossible',
                     'Jason Statham' => 'Crank',
                     'Danzel Washington' => 'Man on Fire'),
               'Comedy' =>
               array ('Charlie Chaplin' => 'City Lights',
                      'Jim Carrey'    => 'Cable Guy',
                      'Rowan Atkinson' => 'The Ultimate Disaster'));
$type_wanted = 'Action'; //You may switch type from Action to Comedy.
$hero_wanted = 'Pearce Brosnan'; // You may switch hero from Pearce Brosnan to Jim Carrey.
print ("$hero_wanted 's  $type_wanted movie is " . $movie_to_watch[$type_wanted][$hero_wanted].".");
// produces browser output as under:
// Pearce Brosnan 's Action movie is Die Another Day.
?>


07-mar-2003 11:28

"Using NULL as a key will evaluate to an empty string. Using an emptry string as key will create (or overwrite) a key with an empty string and its value, it is not the same as using empty brackets."
If you create an array like this:
$foo = array(null => 'bar');
And then want to access 'bar', you must use this syntax:
echo $foo['']; // notice the two single quotes
This will of course cause a fatal error:
echo $foo[];


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