CronHelper

CronHelper.php

<?php
/**
 * A helper class for cronjobs.
 *
 * @author C. Davison
 */
class CronHelper
{
    /**
     * Valid & unique date format strings for each type of cron part.
     * @const MINUTE 
     * @const HOUR
     * @const DAY_OF_MONTH
     * @const MONTH
     * @const DAY_OF_WEEK
     * @see http://php.net/manual/en/function.date.php
     */
    const MINUTE = 'i';
    const HOUR = 'H';
    const DAY_OF_MONTH = 'd';
    const MONTH = 'm';
    const DAY_OF_WEEK = 'N'; 
    /**
     * The default order of a cron, expressed as an array of datetime formats.
     * @static array
     */
    static $part_order = array(
        self::MINUTE,
        self::HOUR,
        self::DAY_OF_MONTH,
        self::MONTH,
        self::DAY_OF_WEEK
    );
    /**
     * Match a cron to a datetime.
     *
     * @param array $cron A list of valid cron expressions in the order given
     * by $part_order.
     * @param \DateTime $datetime The DateTime to be matched.
     * @param array [$part_order=false] The order of the cron parts. If false,
     * this defaults to CronHelper::$part_order.
     * @see CronHelper::matchPart
     * @see CronHelper::$part_order
     */
    static function match(
        array $cron, 
        \DateTime $datetime, 
        $part_order = false
    ) {
        if (count($cron) !== count($part_order)) {
            throw new \LengthException(
                'Length of $cron does not match number of cron parts.'
            );
        }
        // If no order is specified, use the default order
        if (!$part_order) {
            $part_order = self::$part_order;
        }
        // Run through the cron and attempt to match each part to its
        // corresponding datetime part
        for ($i = 0; $i < count($part_order); $i++) {
            $cron_part = $cron[$i];
            $part_type = $part_order[$i];
            $datetime_part = $datetime->format($part_type);
            // If the parts cannot be matched, the whole cron cannot be matched
            if (!self::matchPart($cron_part, $datetime_part, $part_type)) {
                return false;
            }
        }
        return true;
    }
    /**
     * Match a cron part to a part of a timestamp. This presently allows
     * standard cron expressions including:
     *      - '*': matches all values
     *      - ',': for listing values (e.g., 5,10,20)
     *      - '-': for ranges (e.g. 2010-2015)
     *
     * @param mixed $cron_part The cron part to match. 
     * @param mixed $datetime_part The datetime part to match. This should be
     * numerical, and not a textual representation.
     */
    static function matchPart($cron_part, $datetime_part)
    {
        if ($cron_part === '*') return true;
        $subparts = explode(',', $cron_part);
        foreach ($subparts as $subpart) {
            if ($subpart === '*') continue;
            // If there's a hyphen in this subpart, it represents a range of
            // values
            if (strpos($subpart, '-') !== false) {
                $subpart = explode('-', $subpart);
                $end = $subpart[1];
                $start = $subpart[0];
                if ($datetime_part > $start && $datetime_part < $end) continue;
                else return false;
            }
            if ($subpart === $datetime_part) continue;
            // If we get here, the cron part has failed to match the datetime
            // part
            return false;
        }
        return true;
    }
}