php多個進程寫入一個檔案與類比一個隊列

function write_file($filename, $content){    $lock = $filename . '.lck';    $write_length = 0;    while(true) {        if( file_exists($lock) ) {            usleep(100);        } else {            touch($lock);            $write_length = file_put_contents($filename, $content, FILE_APPEND);            break;        }    }    if( file_exists($lock) ) {        unlink($lock);    }    return $write_length;}

class DEQueue {    //儲存    protected $_storage = array();        //入頭    public function unshift($element)    {        return array_unshift($this->_storage, $element);    }        //入尾    public function push($element)    {        return array_push($this->_storage, $element);    }        //出尾    public function pop()    {        return array_pop($this->_storage);    }        //出頭    public function shift()    {        return array_shift($this->_storage);    }        //長度    public function length()    {        return count($this->_storage);    }}