谁能告我这CRON什么意思 我怎么能改吗

<?php
/***************************************************************************
*                            Dolphin Smart Community Builder
*                              -----------------
*     begin                : Mon Mar 23 2006
*     copyright            : (C) 2006 BoonEx Group
*     website              : http://www.boonex.com/
* This file is part of Dolphin - Smart Community Builder
*
* Dolphin is free software. This work is licensed under a Creative Commons Attribution 3.0 License.
* http://creativecommons.org/licenses/by/3.0/
*
* Dolphin is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the Creative Commons Attribution 3.0 License for more details.
* You should have received a copy of the Creative Commons Attribution 3.0 License along with Dolphin,
* see license.txt file; if not, write to marketing@boonex.com
***************************************************************************/
$GLOBALS['bx_profiler_disable'] = true;
define('BX_DOL_CRON_EXECUTE', '1');
$aPathInfo = pathinfo(__FILE__);
require_once ($aPathInfo['dirname'] . '/../inc/header.inc.php');
require_once(BX_DIRECTORY_PATH_INC . 'utils.inc.php');
require_once(BX_DIRECTORY_PATH_INC . 'profiles.inc.php' );
require_once(BX_DIRECTORY_PATH_CLASSES . 'BxDolDb.php');
/*
* This file is used for cron jobs. He is started system cron every minute.
* The file runs jobs at regular intervals. These jobs are listed in `sys_cron_jobs` table.
*
* Fields shark_cron_jobs table:
*  id - key for the table
*  name - job name to be executed
*  time - format of entries are five fields of numbers specifying the minute,
*              hour, day of the month, month and day of the week that a task must be executed.
*
*              * * * * *
*              | | | | |
*              | | | | +--- day of week(0-6 with 0=Sunday)
*              | | | +----- month(1-12)
*              | | +------- day of month(1-31)
*              | +--------- hour(0-23)
*              +----------- minute(0-59)
*
*  class - class name which will run
*  file - path to class file
*  eval - source code which will run
*
* The time numbers can be given as a comma separated list of simple numbers,
* ranges("2-5" is the same as "2,3,4,5"). A single "*" can be used in a field to indicate all
* valid numbers in that field, so it translates to "always". If a given time is valid in all five
* fields then a module function is executed. Here are a few examples that illustrate the possibilities:
*  
*  will run at 16:10:
*  10 16
*  will run at 2:00 on saturday:
*  0 2 * * 6
*  will run at midnight on new years:
*  0 0 1 1 0
*  will run every 15 minutes:
*  *\/15
*  will run at 22:00 on work weekdays:
*  0 22 * * 1-5
*  will run each 23 minutes, 2:00, 4:00 ..., everyday
*  23 0-23/2
*
* Example add new cron job:
*
* 1. Create new class inherited from "BxDolCron" and add method "processing"
*
*      class BxDolCronMy extends BxDolCron {
*      
*          function processing()
*          {
*              // insert code
*          }
*      }
*
* 2. Add record in `sys_cron_jobs` table
*
* @see an example of BxDolCronNotifies, BxDolCronCupid, BxDolCronCmd.
*
*
* Memberships/ACL:
* Doesn't depend on user's membership.
*
*
* Alerts:
* no alerts available
*
*/
function getRange($iLow, $iHigh, $iStep)
{
    $aResult = array();
    for ($i = $iLow; $i <= $iHigh && $iStep; $i += $iStep)
        $aResult[] = $i;
    return $aResult;
}
function getPeriod($sPeriod, $iLow, $iHigh)
{
    $aRes = array();
    $iStep = 1;
    $sErr = '';
   
    do
    {
        if (!$sPeriod)
        {
            $sErr = 'Variable sPeriod is emply';
            break;
        }
        
        $aParam = split('/', $sPeriod);
        
        if (count($aParam) > 2)
        {
            $sErr = 'Error of format for string assigning period';
            break;
        }
            
        if (count($aParam) == 2 && is_numeric($aParam[1]))
            $iStep = $aParam[1];
            
        $sPeriod = $aParam[0];
        
        if ($sPeriod != '*')
        {
            $aParam = split('-', $sPeriod);
            
            if (count($aParam) > 2)
            {
                $sErr = 'Error of format for string assigning period';
                break;
            }
            
            if (count($aParam) == 2)
                $aRes = getRange($aParam[0], $aParam[1], $iStep);
            else
                $aRes = split(',', $sPeriod);
        }
        else
            $aRes = getRange($iLow, $iHigh, $iStep);
    }
    while(false);
   
    if ($sErr)
    {
        // show error or add to log
    }
   
    return $aRes;
}
function checkCronJob($sPeriods, $aDate = array())
{
    $aParam = split(' ', ereg_replace(" +", ' ', trim($sPeriods)));
    $bRes = true;
    if(empty($aDate))
     $aDate = getdate(time());
    for ($i = 0; $i < count($aParam); $i++)
    {
        switch ($i)
        {
            case 0:
                $aRes = getPeriod($aParam[$i], 0, 59);
                $bRes = in_array($aDate['minutes'], $aRes);
                break;
            case 1:
                $aRes = getPeriod($aParam[$i], 0, 23);
                $bRes = in_array($aDate['hours'], $aRes);
                break;
            case 2:
                $aRes = getPeriod($aParam[$i], 1, 31);
                $bRes = in_array($aDate['mday'], $aRes);
                break;
            case 3:
                $aRes = getPeriod($aParam[$i], 1, 12);
                $bRes = in_array($aDate['mon'], $aRes);
                break;
            case 4:
                $aRes = getPeriod($aParam[$i], 0, 6);
                $bRes = in_array($aDate['wday'], $aRes);
                break;
        }
        
        if (!$bRes)
            break;
    }
   
    return $bRes;
}
function runJob($aJob)
{
    if(!empty($aJob['file']) && !empty($aJob['class']) && file_exists(BX_DIRECTORY_PATH_ROOT . $aJob['file'])) {
        if(!class_exists($aJob['class']))
            require_once(BX_DIRECTORY_PATH_ROOT . $aJob['file']);
        
        $oHandler = new $aJob['class']();
        $oHandler->processing();
    }
    else if(!empty($aJob['eval'])) {
        require_once( BX_DIRECTORY_PATH_CLASSES . 'BxDolService.php');
        eval($aJob['eval']);
    }
}
$oDb = new BxDolDb();
$aJobs = $oDb->fromCache('sys_cron_jobs', 'getAll', 'SELECT * FROM `sys_cron_jobs`');
$aDate = getdate(time());
foreach($aJobs as $aRow) {
    if (checkCronJob($aRow['time'], $aDate))
        runJob($aRow);
}
?>

cron 是定时任务，计划任务

能改，转换代码，但你得懂这些代码才可以