PHP array_walk() Function

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:

1. $array: This is a mandatory parameter and specifies the input array.
2. 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.
3. $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 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 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 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:
http://php.net/manual/en/function.array-walk.php