php 文件锁定写入

function file_write($file_name, $text, $mode='a', $timeout=30){  
    $handle = fopen($file_name, $mode);  
    while($timeout>0){  
        if ( flock($handle, LOCK_EX) ) {  
            $timeout--;  
            sleep(1);  
        }  
    }  
    if ( $timeout > 0 ){  
        fwrite($handle, $text.'\n');  
        flock($handle, LOCK_UN);  
        fclose($handle);  
        return true;  
    }  
    return false;  
}