--TEST-- Test array_walk() function : basic functionality - associative array --FILE-- "lemon", "a" => "orange", "b" => "banana", "c" => "apple"); function test_alter(&$item, $key, $prefix) { // dump the arguments to check that they are passed // with proper type var_dump($item); // value var_dump($key); // key var_dump($prefix); // additional argument passed to callback function echo "\n"; // new line to separate the output between each element } function test_print($item, $key) { // dump the arguments to check that they are passed // with proper type var_dump($item); // value var_dump($key); // key echo "\n"; // new line to separate the output between each element } echo "-- Using array_walk with default parameters to show array contents --\n"; var_dump(array_walk($fruits, 'test_print')); echo "-- Using array_walk with one optional parameter to modify contents --\n"; var_dump (array_walk($fruits, 'test_alter', 'fruit')); echo "-- Using array_walk with default parameters to show modified array contents --\n"; var_dump (array_walk($fruits, 'test_print')); echo "Done"; ?> --EXPECT-- *** Testing array_walk() : basic functionality *** -- Using array_walk with default parameters to show array contents -- string(5) "lemon" string(1) "d" string(6) "orange" string(1) "a" string(6) "banana" string(1) "b" string(5) "apple" string(1) "c" bool(true) -- Using array_walk with one optional parameter to modify contents -- string(5) "lemon" string(1) "d" string(5) "fruit" string(6) "orange" string(1) "a" string(5) "fruit" string(6) "banana" string(1) "b" string(5) "fruit" string(5) "apple" string(1) "c" string(5) "fruit" bool(true) -- Using array_walk with default parameters to show modified array contents -- string(5) "lemon" string(1) "d" string(6) "orange" string(1) "a" string(6) "banana" string(1) "b" string(5) "apple" string(1) "c" bool(true) Done