A PHP variable with parentheses?

I don't understand this code:

$outputFunction($dst, $resized, $quality);

It's not a 开发者_如何学编程function e.g myfunction()

It's not a variable e.g $variable = $variable2

What is it?

The code works in the script i have downloaded, i just can't figure out how that piece of code can work...maybe i'm just tired or something..

Thanks.

---

$outputFunction holds the name of the function. Thus, if $outputFunction holds the value "calculate", then calculate($dst, $resized, $quality) is invoked.

---

To add to sbrattla's answer, you can also define anonymous functions in PHP 5.3 (I think), so

$var = function($a) { /* do something */ return $b; }
echo $var(123);

---

These are variable functions.

$outputFunction is evaluated to obtain the name of the function to which the operands will be applied.

There's an entire page dedicated to this topic in the PHP manual.

---

in php you can do something like

$outputFunction = 'myFunction';
$outputFunction(args);

and it works calling the function normally

variable functions

---

The string should initialized some lines before. You can consider this as a pointer of funcrion which allows to change the executed method.

Php will recognize your syntax and will launch the function named in your string (computed one if you want)