WordPress - Checking If You're in the Loop

functions.php

Both theme and plugin developers might need to check if their code is going to be run in the Loop or not. As the name suggests, the in_the_loop() function provides the answer easily.

Usage

<?php
if( in_the_loop() ) {
    // do something loop-related
} else {
    // don't do anything or display some kind of error/warning
}
?>
Probably the easiest one to use among the functions in this article, along with wp_is_mobile().