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PHP : Function Reference : Array Functions : reset

reset

Set the internal pointer of an array to its first element (PHP 4, PHP 5)
mixed reset ( array &array )

reset() rewinds array's internal pointer to the first element and returns the value of the first array element, or FALSE if the array is empty.

Example320.reset() example

<?php

$array
= array('step one', 'step two', 'step three', 'step four');

// by default, the pointer is on the first element
echo current($array) . "<br />\n"; // "step one"

// skip two steps
next($array);
next($array);
echo
current($array) . "<br />\n"; // "step three"

// reset pointer, start again on step one
reset($array);
echo
current($array) . "<br />\n"; // "step one"

?>


See also current(), each(), end(), next(), and prev().

Related Examples ( Source code ) » reset









Code Examples / Notes » reset

kk

When used on a scalar or unset value, reset() spews warning messages. This is often a problem when accessing arrays generated from HTML form input data: these are scalar or unset if the user didn't enter sufficient information.
You can silence these error messages by prefixing an @ (at sign) to reset(), but it is better style to protect your reset() and the following array traversal with an if (isset()). Example code:
if (isset($form_array)) {
 reset($form_array);
 while (list($k, $v) = each($form_array) {
   do_something($k, $v);
 }
}


steffen schomberg

The following method resets every array contained in a multi-dimensional array recursively. It takes the multi-dimensional array as parameter.
function Array_Dimensional_Reset(&$arrRef) {
foreach ($arrRef as $key=>$val) {
if (is_array($val)) {
$this->Array_Dimensional_Reset($val);
reset($arrRef[$key]);
}
}
}


tac

Related to resetting an array is resetting a result set back to the beginning, so you can loop through it again.  To do that, use
mysql_data_seek($result, 0)
I use this often when debugging -- do a query, print it out, then loop through it a second time to process.  I'm adding this here under Reset because that's where I originally looked for this functionality.


leaetherstrip

Note that reset() will not affect sub-arrays of multidimensional array.
For example,
<?php
$arr = array(
1 => array(2,3,4,5,6),
2 => array(6,7,8,9,10)
);

while(list($i,) = each($arr))
{
echo "IN \$arr[$i]
";

while(list($sub_i,$entry) = each($arr[$i]))
{
echo "\$arr[$i][$sub_i] = $entry
";
}
}

reset($arr);
// Do the same again
while(list($i,) = each($arr))
{
echo "IN \$arr[$i]
";

while(list($sub_i,$entry) = each($arr[$i]))
{
echo "\$arr[$i][$sub_i] = $entry
";
}
}
?>
will print
IN $arr[1]
$arr[1][0] = 2
$arr[1][1] = 3
$arr[1][2] = 4
$arr[1][3] = 5
$arr[1][4] = 6
IN $arr[2]
$arr[2][0] = 6
$arr[2][1] = 7
$arr[2][2] = 8
$arr[2][3] = 9
$arr[2][4] = 10
IN $arr[1]
IN $arr[2]


27-feb-2006 09:20

I wrote a nice function, which rotates values of array. Very useful for table rows where you have to rotate colors
<?php
function rotate(&$array) {
   $item = current($array);
   if (!next($array)) reset($array);  
   return $item;
}
?>


colin

I had a problem with PHP 5.0.5 somehow resetting a sub-array of an array with no apparent reason.  The problem was in doing a foreach() on the parent array PHP was making a copy of the subarrays and in doing so it was resetting the internal pointers of the original array.
The following code demonstrates the resetting of a subarray:
<?
$a = array(
   'a' => array(
       'A', 'B', 'C', 'D',
   ),
   'b' => array(
       'AA', 'BB', 'CC', 'DD',
   ),
);
// Set the pointer of $a to 'b' and the pointer of 'b' to 'CC'
reset($a);
next($a);
next($a['b']);
next($a['b']);
next($a['b']);
var_dump(key($a['b']));
foreach($a as $k => $d)
{
}
var_dump(key($a['b']));
?>
The result of the two var dumps are 3 and 0, respectively.  Clearly the internal pointer of $a['b'] was reset by doing the foreach loop over $a.
Each time the foreach loop iterated over the 'a' and 'b' keys of $a it made a copy of $a['a'] and $a['b'] into $d which resetted the internal pointers of $a['a'] and $a['b'] despite making no obvious changes.
The solution is instead to iterate over the keys of $a.
<?
foreach(array_keys($a) as $k)
{
}
?>
and using $a[$k] (or creating an alias of $a[$k] as $d and dealing with the consequences of using aliases).
For the curious, I was implementing the Iterator interface on a dummy object and calling a global object to do the actual iteration (also to cope with PHP's lack of C-style pointers which when doing a $a = $b on objects would cause the data in $a to be inconsistent with the data in $b when modified).  Being that I had many dummy objects representing different data sets I chose to store each data set as a subarray contained within the global object.  To make this work each dummy object has to store a key (which can freely be duplicated without problems) that it passes to the global object when rewind, key, current, next, and valid were called on the dummy object.
Unfortunately for me, my key required to be more than just a simple string or number (if it was then it could be used to directly index the subarray of data for that object and problem avoided) but was an array of strings.  Instead, I had to iterate over (with a foreach loop) each subarray and compare the key to a variable stored within the subarray.
So by using a foreach loop in this manner and with PHP resetting the pointer of subarrays it ended up causing an infinite loop.
Really, this could be solved by PHP maintaining internal pointers on arrays even after copying.


kevin

Here is a simple example on how to combine 2 arrays. Here we use array_combine() to create list of months and there respective month number. The same result could just as easily be achieved with array('1'=>'January') etc.
<?php
                                                                                                             
 // make it or break it
 error_reporting(E_ALL);
                                                                                                             
 // create and array of keys
 $keys = range(1,12);
                                                                                                             
 // create an array of months
 $months = array(
 'January',
 'February',
 'March',
 'April',
 'May',
 'June',
 'July',
 'August',
 'September',
 'October',
 'November',
 'December'
);
                                                                                                             
 // combine the arrays
 $combined_array = array_combine($keys, $months);
                                                                                                             
 // echo out the results
 foreach($combined_array as $k=>$v){ echo $k.' -> '.$v.'<br />'; }
                                                                                                             
?>


m dot lebkowski+php

Colin, there`s a better (IMO) way to solve your problem.
<?  
 // ...
 foreach($a as $k => &$d){}   // notice the "&"
 // ...
?>
It`s a new feature in PHP5 to use references in foreach loop. This way PHP isn`t making a copy of the array, so the internal pointer won`t be reset.


s_p_a_mcatcher

Be aware that when using reset() to clear an element and key from an array, if auto-incrementing, the new array keys will not reset a key previously set:
$temparray[] = "0";
$temparray[] = "1";
$temparray[] = "2";
unset($temparray[2]);
$temparray[] = "2";
$temparray[] = "3";
print_r($temparray);
The above will return:
Array
(
   [0] => 0
   [1] => 1
   [3] => 2
   [4] => 3
)
When attempting something like this, its better to use array_pop().
hope it helped


jules

Be aware that if you give an empty array to reset(), what you'll get back is a boolean. consider...
     $myarray = array();
     $ret = reset($myarray);
     echo 'reset has type '. gettype($ret) .' and val * '. $ret;
     if( $ret )
     {
       echo '*. But it evaluates true';
     }
     else
     {
       echo '*. It evaluates false';
     }
     if( is_null($ret) )
     {
       echo ', and appears null';
     }
     {
       echo ', and appears not null';
     }
     
     echo '.';
<output>
reset has type boolean and val * *. It evaluates false, and appears not null.
</output>
<bleaugh/>


alexandre koriakine

Also it's good to reset this way the multidimentional arrays:
reset($voo2['moder']);
while (list($key, $value) = each ($voo2['moder'])) {
reset($voo2['moder'][$key]);
while (list($key1, $value1) = each ($voo2['moder'][$key])) {
#do what u want
}
}


02-jul-2001 03:30

A cleaner (better?) way would be to use is_array() instead:
if (is_array($form_array)) {
[array stuff here]
}


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