Question

Consider this snippet:

function f() {
    return 'hi';
}

echo f();

Vs this snippet:

echo f();

function f() {
    return 'hi';
}

When I run the scripts, they both produce the same results. That’s great.

But my question is (and I could not find a good answer or reference in any of my searches), is it okay to call the function before it is defined (ie, from a sequential parsing of the script file perspective)?

I don’t want to run into any issues or deprecation down the road if I leave the function call ahead of the function definition block in my script file.

Answer 1

From the Manual:

Functions need not be defined before
they are referenced, except when a
function is conditionally defined as
shown in the two examples below.

The possibility to call (reference) a function before it is defined is a PHP intentional feature and I don’t think you need to worry about it becoming deprecated.

As an observation, if you can choose from declaring the function before or after, it would be common sense to declare it before it’s used.

Note: The following code will give a fatal error because the function will only be defined at run rime.

<?php
echo helloWorld();
if(1){
    function helloWorld() {
        return 'hello world';
    }
}
?>