--TEST-- Test array_key_exists() function : usage variations - array keys are different data types --FILE-- array( 0 => 'zero', 1 => 'one', 12345 => 'positive', -2345 => 'negative', ), // boolean data /*4*/ 'bool lowercase' => array( true => 'lowert', false => 'lowerf', ), // empty data /*5*/ 'empty single quotes' => array( '' => 'emptys', ), // string data /*6*/ 'string' => array( "stringd" => 'stringd', 'strings' => 'strings', $heredoc => 'stringh', ), ); // loop through each element of $inputs to check the behavior of array_key_exists() $iterator = 1; foreach($inputs as $type => $input) { echo "\n-- $type data --\n"; //iterate over again to get all different key values foreach ($inputs as $new_type => $new_input) { echo "-- \$key arguments are $new_type data:\n"; foreach ($new_input as $key => $search) { var_dump(array_key_exists($key, $input)); } } $iterator++; }; echo "Done"; ?> --EXPECT-- *** Testing array_key_exists() : usage variations *** -- int data -- -- $key arguments are int data: bool(true) bool(true) bool(true) bool(true) -- $key arguments are bool lowercase data: bool(true) bool(true) -- $key arguments are empty single quotes data: bool(false) -- $key arguments are string data: bool(false) bool(false) bool(false) -- bool lowercase data -- -- $key arguments are int data: bool(true) bool(true) bool(false) bool(false) -- $key arguments are bool lowercase data: bool(true) bool(true) -- $key arguments are empty single quotes data: bool(false) -- $key arguments are string data: bool(false) bool(false) bool(false) -- empty single quotes data -- -- $key arguments are int data: bool(false) bool(false) bool(false) bool(false) -- $key arguments are bool lowercase data: bool(false) bool(false) -- $key arguments are empty single quotes data: bool(true) -- $key arguments are string data: bool(false) bool(false) bool(false) -- string data -- -- $key arguments are int data: bool(false) bool(false) bool(false) bool(false) -- $key arguments are bool lowercase data: bool(false) bool(false) -- $key arguments are empty single quotes data: bool(false) -- $key arguments are string data: bool(true) bool(true) bool(true) Done