Question

I’m just trying to figure out why I can’t do this:

<?php
$a = "echo";
$a("test");
?>

It just returns PHP Fatal error: Call to undefined function echo() in Command line code on line 1

When I can do this:

<?php
$a = "explode";
var_dump($a("|","1|2|3"));
?>

and get the expected result.

Edit: Found a solution to my problem (as inspired by the various answers below).
Create an anonymous function inside the variable $a as so:

$a = function($a){echo $a;};

This will only work in PHP 5.3 or greater though.

Answer 1

That’s because echo is not a function but a language construct.

Try with print() instead. That should work fine.

EDIT: As pointed out in the comments print is also a language construct and won’t work! Only solution is wrapping echo or print in a user defined function then.

<?php
function output($str){ 
    return print $str;
}

$a = "output";
$a("Lorem Ipsum ...");
?>