PHP array_walk() Function
Last Updated :
11 Jul, 2025
The
array_walk() function is an inbuilt function in PHP. The array_walk() function walks through the entire array regardless of pointer position and applies a callback function or user-defined function to every element of the array. The array element's keys and values are parameters in the callback function.
Syntax:
boolean array_walk($array, myFunction, $extraParam)
Parameters: This function accepts three parameters as described below:
-
$array: This is a mandatory parameter and specifies the input array.
- myFunction: This parameter specifies the name of the user-defined function and is also mandatory. The user-defined function generally excepts two parameters of which the first parameter represent the array's values and the second parameter represents the corresponding keys.
- $extraparam: This is an optional parameter. It specifies an extra parameter to the user-defined function in addition to the two parameters, array keys and values.
Return value: This function returns a boolean value. It returns TRUE on success or FALSE on failure.
Below programs illustrate the array_walk() function:
Program 1:
PHP
<?php
// PHP program to illustrate array_walk()
// function
// user-defined callback function
function myfunction($value, $key)
{
echo "The key $key has the value $value \n";
}
// Input array
$arr = array("a"=>"yellow", "b"=>"pink", "c"=>"purple");
// calling array_walk() with no extra parameter
array_walk($arr, "myfunction");
?>
Output:
The key a has the value yellow
The key b has the value pink
The key c has the value purple
Program 2:
PHP
<?php
// PHP program to illustrate array_walk()
// function
// user-defined callback function
function myfunction($value, $key, $extraParam)
{
echo "The key $key $extraParam $value \n";
}
// Input array
$arr = array("a"=>"yellow", "b"=>"pink", "c"=>"purple");
// calling array_walk() with extra parameter
array_walk($arr, "myfunction", "has the value");
?>
Output:
The key a has the value yellow
The key b has the value pink
The key c has the value purple
Program 3:
php
<?php
// PHP program to illustrate array_walk()
// function
// user-defined callback function to
// update array values - to update array
// values, pass the first parameter by reference
function myfunction(&$value, $key)
{
$value = $value + 10;
}
// Input array
$arr = array("first"=>10, "second"=>20, "third"=>30);
// calling array_walk() with no extra parameter
array_walk($arr, "myfunction");
// printing array after updating values
print_r($arr);
?>
Output:
Array
(
[first] => 20
[second] => 30
[third] => 40
)
Reference:
https://www.php.net/manual/en/function.array-walk.php
