How to implement PHP process lock

<?php
/**
 * CacheLock 进程锁,主要用来进行cache失效时的单进程cache获取，防止过多的SQL请求穿透到数据库
 * 用于解决PHP在并发时候的锁控制,通过文件/eaccelerator进行进程间锁定
 * 如果没有使用eaccelerator则进行进行文件锁处理，会做对应目录下产生对应粒度的锁
 * 使用了eaccelerator则在内存中处理，性能相对较高
 * 不同的锁之间并行执行，类似mysql innodb的行级锁
 * 本类在sunli的phplock的基础上做了少许修改  http://code.google.com/p/phplock
 * @author yangxinqi
 *
 */
namespace Common\Business;


class PhpLock
{
    //文件锁存放路径
    private $path = null;
    //文件句柄
    private $fp = null;
    //锁粒度,设置越大粒度越小
    private $hashNum = 100;
    //cache key
    private $name;
    //是否存在eaccelerator标志
    private  $eAccelerator = false;

    /**
     * 构造函数
     * 传入锁的存放路径，及cache key的名称，这样可以进行并发
     * @param string $path 锁的存放目录，以"/"结尾
     * @param string $name cache key
     */
    public function __construct($name,$path=&#39;lock\\&#39;)
    {
        $app_path = str_replace(&#39;ThinkPHP/&#39;, &#39;&#39;, THINK_PATH);
        $is_cli = php_sapi_name();
        if($is_cli == &#39;cli&#39; || $is_cli == &#39;cli_server&#39;)
        {
            $app_path = trim(APP_PATH, &#39;.&#39;);
        }
        else
        {
            $app_path = $app_path . trim(APP_PATH, &#39;.&#39;);
        }

        $path = $app_path.&#39;/Common/Business/lockfile/&#39;;
        if(!file_exists($path))
        {
            mkdir($path);
            chmod($path,777);
        }
        //$path .= &#39;/protected/runtime/cache/&#39;;
        //判断是否存在eAccelerator,这里启用了eAccelerator之后可以进行内存锁提高效率
        $this->eAccelerator = function_exists("eaccelerator_lock");
        if(!$this->eAccelerator)
        {
            //$this->path = $path.($this->_mycrc32($name) % $this->hashNum).&#39;.txt&#39;;
            $this->path = $path.sha1($name).&#39;.txt&#39;;
        }
        $this->name = $name;
    }

    /**
 * crc32
 * crc32封装
 * @param int $string
 * @return int
 */
    private function _mycrc32($string)
    {
        $crc = abs (crc32($string));
        if ($crc & 0x80000000) {
            $crc ^= 0xffffffff;
            $crc += 1;
        }
        return $crc;
    }
    /**
     * 加锁
     * Enter description here ...
     */
    public function lock()
    {
        //如果无法开启ea内存锁，则开启文件锁
        if(!$this->eAccelerator)
        {
            //配置目录权限可写
            $this->fp = fopen($this->path, &#39;w+&#39;);
            if($this->fp === false)
            {
                return false;
            }
            return flock($this->fp, LOCK_EX);
        }else{
            return eaccelerator_lock($this->name);
        }
    }

    /**
     * 解锁
     * Enter description here ...
     */
    public function unlock()
    {
        if(!$this->eAccelerator)
        {
            if($this->fp !== false)
            {
                flock($this->fp, LOCK_UN);
                clearstatcache();
            }
            //进行关闭
            fclose($this->fp);
        }else{
            return eaccelerator_unlock($this->name);
        }
    }
}

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