PHP中实现crontab代码分享

1. 准备一个标准crontab文件 ./crontab

# m h dom mon dow command

* * * * * date > /tmp/cron.date.run

2. crontab -e 将此cron.php脚本加入系统cron

* * * * * /usr/bin/php cron.php

3. cron.php 源码

// 从./crontab读取cron项，也可以从其他持久存储（mysql、redis）读取

$crontab = file('./crontab');

$now = $_SERVER['REQUEST_TIME'];
foreach ( $crontab as $cron ) {

 $slices = preg_split("/[\s]+/", $cron, 6);

 if( count($slices) !== 6 ) continue;
 $cmd       = array_pop($slices);

 $cron_time = implode(' ', $slices);

 $next_time = Crontab::parse($cron_time, $now);

 if ( $next_time !== $now ) continue; 
 $pid = pcntl_fork();

 if ($pid == -1) {

  die('could not fork');

 } else if ($pid) {

  // we are the parent

  pcntl_wait($status, WNOHANG); //Protect against Zombie children

 } else {

      // we are the child

  `$cmd`;

  exit;

 }

}
/* https://github.com/jkonieczny/PHP-Crontab */

class Crontab {

   /**

 * Finds next execution time(stamp) parsin crontab syntax,

 * after given starting timestamp (or current time if ommited)

 *

 * @param string $_cron_string:

 *

 * 0 1 2 3 4

 * * * * * *

 * - - - - -

 * | | | | |

 * | | | | +----- day of week (0 - 6) (Sunday=0)

 * | | | +------- month (1 - 12)

 * | | +--------- day of month (1 - 31)

 * | +----------- hour (0 - 23)

 * +------------- min (0 - 59)

 * @param int $_after_timestamp timestamp [default=current timestamp]

 * @return int unix timestamp - next execution time will be greater

 * than given timestamp (defaults to the current timestamp)

 * @throws InvalidArgumentException

 */

    public static function parse($_cron_string,$_after_timestamp=null)

    {

        if(!preg_match('/^((\*(\/[0-9]+)?)|[0-9\-\,\/]+)\s+((\*(\/[0-9]+)?)|[0-9\-\,\/]+)\s+((\*(\/[0-9]+)?)|[0-9\-\,\/]+)\s+((\*(\/[0-9]+)?)|[0-9\-\,\/]+)\s+((\*(\/[0-9]+)?)|[0-9\-\,\/]+)$/i',trim($_cron_string))){

            throw new InvalidArgumentException("Invalid cron string: ".$_cron_string);

        }

        if($_after_timestamp && !is_numeric($_after_timestamp)){

            throw new InvalidArgumentException("\$_after_timestamp must be a valid unix timestamp ($_after_timestamp given)");

        }

        $cron = preg_split("/[\s]+/i",trim($_cron_string));

        $start = empty($_after_timestamp)?time():$_after_timestamp;
        $date = array( 'minutes' =>self::_parseCronNumbers($cron[0],0,59),

                            'hours' =>self::_parseCronNumbers($cron[1],0,23),

                            'dom' =>self::_parseCronNumbers($cron[2],1,31),

                            'month' =>self::_parseCronNumbers($cron[3],1,12),

                            'dow' =>self::_parseCronNumbers($cron[4],0,6),

                        );

        // limited to time()+366 - no need to check more than 1year ahead

        for($i=0;$i<=60*60*24*366;$i+=60){

            if( in_array(intval(date('j',$start+$i)),$date['dom']) &&

                in_array(intval(date('n',$start+$i)),$date['month']) &&

                in_array(intval(date('w',$start+$i)),$date['dow']) &&

                in_array(intval(date('G',$start+$i)),$date['hours']) &&

                in_array(intval(date('i',$start+$i)),$date['minutes'])
                ){

                    return $start+$i;

            }

        }

        return null;

    }
    /**

 * get a single cron style notation and parse it into numeric value

 *

 * @param string $s cron string element

 * @param int $min minimum possible value

 * @param int $max maximum possible value

 * @return int parsed number

 */

    protected static function _parseCronNumbers($s,$min,$max)

    {

        $result = array();
        $v = explode(',',$s);

        foreach($v as $vv){

            $vvv = explode('/',$vv);

            $step = empty($vvv[1])?1:$vvv[1];

            $vvvv = explode('-',$vvv[0]);

            $_min = count($vvvv)==2?$vvvv[0]:($vvv[0]=='*'?$min:$vvv[0]);

            $_max = count($vvvv)==2?$vvvv[1]:($vvv[0]=='*'?$max:$vvv[0]);
            for($i=$_min;$i<=$_max;$i+=$step){

                $result[$i]=intval($i);

            }

        }

        ksort($result);

        return $result;

    }

}