gistfile1.php

<?php 
function first($param)
{
    try {
        // Some logic with $param here
        throw new CustomException();
    } catch (CustomException $e) {
        // This particular exception
        // is really bad and needs to 
        // stop everything
        $logger->log($e->getMessage());
    }
}

function two()
{
    // ... Logic
    $return = first($someParam);
    // This logic can't happen without a valid return from $return
}