In this article, you will learn about callable keyword in PHP. The callable keyword in PHP is used to force a function argument to be a reference to a function.
examples of the CALLABLE keyword
Example 1. In this example, we use callable to require a callback function as an argument.
<?php
function printFormatted(callable $format, $str) {
echo $format($str);
echo "<br>";
}
function exclaim($str) { return $str . "!"; }
printFormatted("exclaim", "Hello World");
?>
