array_walk Apply a user function to every member of an array &reftitle.description; boolarray_walk arrayarray callablecallback mixeduserdata&null; 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. &reftitle.parameters; array The input array. callback Typically, callback takes on two parameters. The array parameter's value being the first, and the key/index second. If callback needs to be working with the actual values of the array, specify the first parameter of callback as a reference. Then, any changes made to those elements will be made in the original array itself. 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. &reftitle.returnvalues; &return.success; &reftitle.errors; 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. &reftitle.examples; "lemon", "a" => "orange", "b" => "banana", "c" => "apple"); function test_alter(&$item1, $key, $prefix) { $item1 = "$prefix: $item1"; } function test_print($item2, $key) { echo "$key. $item2
\n"; } echo "Before ...:\n"; array_walk($fruits, 'test_print'); array_walk($fruits, 'test_alter', 'fruit'); echo "... and after:\n"; array_walk($fruits, 'test_print'); ?> ]]> &example.outputs; &reftitle.seealso; array_walk_recursive iterator_apply list each call_user_func_array array_map &seealso.callback; &foreach;