Quick & dirty loop with pcntl_fork

loop.php

<?php

// every thing before will be used in every child process

while(true) {       
    $pid = pcntl_fork();

    if ($pid === -1) {
        die('Could not fork process');
    } elseif ($pid) {
        // parent wait for child to end
        // only the parent will keep staying in the loop
        // forking again after 5 minutes when previous child ended
        pcntl_wait($status);
        sleep(5 * 60);
    } else {
        // child gets out of the while loop to execute next code and terminate after
        // child will never loop nor fork
        break;
    }
}

// following script will repeat itself after 5 minutes
doSomething();

For the record this has been used in a preprod environment to simulate a crontab without having to actually do a crontab