php man page for array_walk

ARRAY_WALK(3)								 1							     ARRAY_WALK(3)

array_walk - Apply a user supplied function to every member of an array

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

DESCRIPTION
	Applies the user-defined $callback function to each element of the $array array.

       array_walk(3)  is  not  affected  by  the  internal array pointer of $array. array_walk(3) will walk through the entire array regardless of
       pointer position.

PARAMETERS
	      o $array
		- The input array.

	      o $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 of $callback as  a  refer-
		     ence. Then, any changes made to those elements will be made in the original array itself.

	      Note

		      Many  internal  functions  (for example strtolower(3)) 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 unpre-
	      dictable.

	      o $userdata
		- If the optional $userdata parameter is supplied, it will be passed as the third parameter to the $callback.

RETURN VALUES
	Returns TRUE on success or FALSE on failure.

ERRORS
/EXCEPTIONS
	If function $callback requires more parameters than given to it, an error of level  E_WARNING will be generated  each  time  array_walk(3)
       calls $callback.

EXAMPLES
       Example #1

	      array_walk(3) 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 />
";
	      }

	      echo "Before ...:
";
	      array_walk($fruits, 'test_print');

	      array_walk($fruits, 'test_alter', 'fruit');
	      echo "... and after:
";

	      array_walk($fruits, 'test_print');
	      ?>

	      The above example will output:

	      Before ...:
	      d. lemon
	      a. orange
	      b. banana
	      c. apple
	      d. fruit: lemon
	      a. fruit: orange
	      b. fruit: banana
	      c. fruit: apple

SEE ALSO
       array_walk_recursive(3),  iterator_apply(3),  list(3), each(3), call_user_func_array(3), array_map(3), information about the callback type,
       foreach.

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