PHP callable Keyword

Example

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");
?>

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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

Example

Using different types of callables:

<?php
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");
?>

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❮ PHP Keywords