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(PHP 4, PHP 5)
array_walk — Apply a user function to every member of an array
Applies the user-defined callback
function to each
element of the array
array.
array_walk() is not affected by the internal array
pointer of array
. array_walk()
will walk through the entire array regardless of pointer position.
array
The input array.
callback
Typically, callback
takes on two parameters.
The array
parameter's value being the first, and
the key/index second.
Note:
If
callback
needs to be working with the actual values of the array, specify the first parameter ofcallback
as a reference. Then, any changes made to those elements will be made in the original array itself.
Note:
Many internal functions (for example strtolower()) will throw a warning if more than the expected number of argument are passed in and are not usable directly as a
callback
.
Only the values of the array
may potentially be
changed; its structure cannot be altered, i.e., the programmer cannot
add, unset or reorder elements. If the callback does not respect this
requirement, the behavior of this function is undefined, and
unpredictable.
userdata
If the optional userdata
parameter is supplied,
it will be passed as the third parameter to the
callback
.
Returns TRUE
on success or FALSE
on failure.
If function callback
requires more parameters than
given to it, an error of level
E_WARNING will be generated each time array_walk()
calls callback
.
Example #1 array_walk() example
<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");
function test_alter(&$item1, $key, $prefix)
{
$item1 = "$prefix: $item1";
}
function test_print($item2, $key)
{
echo "$key. $item2<br />\n";
}
echo "Before ...:\n";
array_walk($fruits, 'test_print');
array_walk($fruits, 'test_alter', 'fruit');
echo "... and after:\n";
array_walk($fruits, 'test_print');
?>
The above example will output:
Before ...: d. lemon a. orange b. banana c. apple ... and after: d. fruit: lemon a. fruit: orange b. fruit: banana c. fruit: apple