Php Callable Function

calendar2022-03-12 · 1 min read · php php-coding  ·
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Callbacks can be denoted by the "callable" type declaration.

Example:

 1icasimpan$ nl -ba callable_example.php
 2     1	<?php
 3     2	function printFormatted(callable $format, $str) {
 4     3	  echo $format($str);
 5     4	  echo "<br>";
 6     5	}
 7     6	
 8     7	function exclaim($str) { return $str . "!"; }
 9     8	printFormatted("exclaim", "Hello World");
10     9	?>

This outputs "Hello World!".

  • Line 7 is the callable function "exclaim"
  • Line 2 is the function "printFormatted" with callable function parameter
  • Line 8 triggers the function "printFormated" which basically pass the name 'in plain string' with the parameter "Hello World"

NOTES

  • Line 2 function "printFormatted" parameters are actually the signature of the callable function. See line 3
  • Means by which callable function is called is via "echo". See line 3
  • Line 7 is the callable function
  • Line 8 is the call to function that calls the callable function "exclaim".

See further details in https://www.php.net/manual/en/language.types.callable.php and https://www.w3schools.com/php/keyword_callable.asp