多个进程读取同一文件的PHP

Question

I have a little problem inside my application. I have many process launched automatically, from the server with crontab, written in php to read file inside a folder.

Sometimes different process read the same file and create a problem inside the application. Is there a way to manage this problem? Actually I read all files inside a folder, read each of them and delete immediately, but sometimes another process read the same file before I delete It.

This is my script written with cakephp3 (so some classes like File is only for cakephp3 but isn't the point of the question) to read and delete:

$xml_files = glob(TMP . 'xml/*.xml');
foreach($xml_files as $fileXml)
{
   //read the file and put into a string or array or object
    $explStr = explode('/', $fileXml);
    $filename = $explStr[count($explStr) - 1];
    $path = TMP . '/xml/' . $filename;
    $file = new File($path, false);

    if($file->exists()){
        $string = $file->read();

        $file->close();
        $file->delete();
    }
}   

Answer 1

使用flock()获取（或尝试获取）文件锁并采取相应的措施。

Answer 2

It's called a race condition, and when working with files you could lock the file when process A uses it, it locks it, then other processes would check if it's locked and if it is then do nothing. Then unlock the file when process A has finished with it.