NULL, 'empty' => '', 'zero' => 0, 'space' => ' ', 'character' => 'X', 'true' => TRUE, 'false' => FALSE, ); print_r(''); // We merge in 'undefined' so we have it as a key. foreach(array_merge($array, array('undefined' => 1)) as $key => $dont_use) { print_r(''); } print_r('

'.implode('	',array( 'Key', 'array_key_exists()', 'isset()', 'empty()', 'is_null()' )).'
'.implode('	',array( '$array[\''.$key.'\']', var_export(array_key_exists($key, $array),true), var_export(isset($array[$key]),true), var_export(empty($array[$key]),true), var_export(is_null($array[$key]),true) )).'

');