PHP array_walk() Function

PHP array_walk() Function

The array_walk() function in PHP is used to apply the user-defined callback function to each element of the array. This function returns a Boolean TRUE on success or FALSE on failure.

Syntax

array_walk ( array &$array , callable $callback [, mixed $userdata = NULL ] )

Parameter

array(required)- This array represents the input array.

callable(required)- It takes two parameters. The first one is the array parameter's value, and the second one is the key/index.

userdata(optional)- This parameter represents an extra parameter, and it will be passed as the third parameter to the callback. The default value is null.

Return

This function returns a Boolean value TRUE on success or FALSE on failure.

Error/Exception

This function throwsan ArgumentCountError if the callback function requires more than 2 parameters

Example 1

 "lemon", "2" => "orange", "3" => "banana", "4" => "apple");
 //initializing the function
 function myfunction($item2, $key)
 {
     echo "$key. $item2\n";
 }
 echo "The array_walk() function ...\n";
 //Applying the user-defined callback function to each element of the array 
 array_walk($fruits, 'myfunction');
 ?> 

Output

The array_walk() function ...:
 1. lemon
 2. orange
 3. banana
 4. apple 

Example 2

"red","b"=>"green","c"=>"blue");
 //Applying the user-defined callback function to each element of the array 
 array_walk($array,"myfunction","has the value");
 ?> 

Output

The key 'a' has the value red
The key 'b' has the value green
The key 'c' has the value blue 

Example 3

 'Reema', 'b' => 'Raj', 'c'=>'Monica');
//initializing the function
function myFunction($item, $key)
{
    echo "The $key holds $item\n";
}
//Applying the user-defined callback function to each element of the array 
array_walk($name, 'myFunction');
?> 

Output

The a holds Reema
The b holds Raj
The c holds Monica 

Example 4

"Reema","Age"=>"21","Institute"=>"TutorialAndExample");
//passing function as null
print_r(array_walk($a,null));//will return an error as it required valid callable function
?> 

Output

PHP Warning:  array_walk() expects parameter 2 to be a valid callback, no array or string given in /workspace/Main.php on line 3