<?php

class Cron
{
    private $fileName;

    protected static $instance;

    public static function init($fileName = 'cache_cron')
    {
        if(!self::$instance) {
            self::$instance = new self( $fileName );
        }

        return self::$instance;
    }

    private function __construct($fileName)
    {
        $this->fileName = __DIR__ . DIRECTORY_SEPARATOR . $fileName;
    }

    private function __clone() {}

    public function runEvery($time)
    {
        if( !(file_exists($this->fileName) && ((filemtime($this->fileName) + $time) >= time())) ) {
            $this->setExecuted();

            return true;
        }

        return false;
    }

    public function setExecuted()
    {
        touch($this->fileName);
    }
}

// 5 - кол секунд для повторного выполнения
if( Cron::init()->runEvery(5) ) {
    var_dump('Run baby run');
}