在表单处理过程中如何避免使用if`语句？

Question

On each example of form processing I found this scenario:

if(!empty($_POST)) {... 

... and than - so many lines (sometimes about 250) which belongs to the above if.
Very unsuitable to track.

Is there a way like this:
if(empty($_POST)) {show show some message or echo... anything}, and then - stop the code
So all next lines will be outside of very long if and they'll still execute only if that if is satisfied.

I tried something, but the members of $_POST (username, pass...) in this case are not available.

Answer 1

Define a function that will execute the code necessary and pass the $_POST variable as an argument. In that way the required variables (e.g. username, password) are now available in the function

function executePost($post) {
   // execute code here with $post variables
   $username = $post['username'];
   $password = $post['password'];
}

You call the function after you checked the post

if(!empty($_POST)) {
    executePost($_POST);
} else {
   echo 'Post was empty';
}