In many cases when developing functions, you might reuse the same library of functions in other projects. Also, if you work with a team, your code might be used by other developers. In order to control the use of your code, it might be appropriate to make use of a type hint. This involves specifying the data type your function expects for that particular parameter.
Parameters in functions can be prefixed by a type hint. The following type hints are available in both PHP 5 and PHP 7:
Array
Class
Callable
If a call to the function is made, and the wrong parameter type is passed, a
TypeError
is thrown. The following example requires an array, an instance ofDateTime
, and an anonymous function:function someTypeHint(Array $a, DateTime $t, Callable $c) { $message = ''; $message .= 'Array Count: ' . count($a) . PHP_EOL; $message .= 'Date: ' . $t->format('Y-m-d') . PHP_EOL; $message .= 'Callable Return: ' . $c() . PHP_EOL; return $message; }