PHP中如何实现crontab代码

PHP是一种通用开源脚本语言。语法吸收了C语言、Java和Perl的特点，利于学习，使用广泛，主要适用于Web开发领域。下面，小编为大家搜索整理了PHP中如何实现crontab代码，希望能给大家带来帮助!更多精彩内容请及时关注我们应届毕业生考试网!

　　1. 准备一个标准crontab文件 ./crontab

代码如下:

# m h dom mon dow command

* * * * * date > /tmp/

　　2. crontab -e 将此脚本加入系统cron

代码如下:

* * * * * /usr/bin/php

　　3. 源码

代码如下:

// 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;

}

}

/* */

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;

}

}