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PHP callable Keyword

❮ PHP Keywords


Use callable to require a callback function as an argument:

function printFormatted(callable $format, $str) {
  echo $format($str);
  echo "<br>";

function exclaim($str) { return $str . "!"; }
printFormatted("exclaim", "Hello World");
Try it Yourself »

Definition and Usage

The callable keyword is used to force a function argument to be a reference to a function.

A callable can be one of the following:

  • An anonymous function
  • A string containing the name of a function
  • An array describing a static class method
  • An array describing an object method

More Examples


Using different types of callables:

function printFormatted(callable $format, $str) {
  echo $format($str);
  echo "<br>";

class MyClass {
  public static function ask($str) {
    return $str . "?";
  public function brackets($str) {
    return "[$str]";

// An anonymous function
$func = function($str) { return substr($str, 0, 5); };
printFormatted($func , "Hello World");

// A string containing the name of a function
printFormatted("strtoupper", "Hello World");

// An array describing a static class method
printFormatted(["MyClass", "ask"], "Hello World");

// An array describing an object method
$obj = new MyClass();
printFormatted([$obj, "brackets"], "Hello World");
Try it Yourself »

❮ PHP Keywords