Stringable
stringable is a type, which represents data that may be used as a string: either a string, a heredoc or a string constant; or an object which has the __toString() method.
Stringable is automatically added to any class and subclasses that has the __toString() method, though it is recommended to add it explicitly.
<?php
function foo(Stringable $s) {
print $s;
}
class MyString implements Stringable {
function __toString() {
return __METHOD__;
}
}
foo('foo'); // foo
foo(new X()); // MyString::__toString
?>