Pure PHP

PHP Command Line - Avoid several Instances of your App.

Since PHP 4, you can also write command line apps in php. If you have a critical app, and you want to avoid several, or mor than one instance of your app, to run, you can use the following class. It works only on unix and linux operating sytems.

Usage:

<?php
inlude("ProcessHandler.class.php");
if(ProcessHandler::isActive()){
   die("Already running!\n");
}else{
   ProcessHandler::activate();
   //run my app
}
?>

<?php
if (!defined('PID')) {
    define("PID","/tmp/pid.php");
}
class ProcessHandler{
    function isActive(){
        $pid = ProcessHandler::getPID();
        if($pid == null){
            $ret = false;
        }else{
            $ret = posix_kill ( $pid, 0 );
        }
        if($ret == false){
            ProcessHandler::activate();
        }
        return $ret;
    }
    function activate(){
        $pidfile = PID;
        $pid = ProcessHandler::getPID();
        if($pid != null && $pid == getmypid()){
            return "Already running!\n";
        }else{
            $fp = fopen($pidfile,"w+");
            if($fp){
                if(!fwrite($fp,"<"."?php\n\$pid = ".getmypid().";\n?".">")){
                    die("Can not create pid file!\n");
                }
                fclose($fp);
            }else{
                die("Can not create pid file!\n");
            }
        }
    }
    function getPID(){
        if(file_exists(PID)){
            require(PID);
            return $pid;
        }else{
            return null;
        }
    }
}
?>

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PHP Command Line - Avoid several Instances of your App.

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