cakephp 3锁定文件属性

Question

I have an application that create many php process to read file. Sometimes process read the same file so I need to lock file when a process read It.

The application need to read only one times a file and after delete It. Sometimes two process read the same file and this is a big problem.

I have create many process that every one loop through a folder, read all file, and delete it. I don't want that two process read the same file, but the problem is that the process works simultaneously.

code of every process :

public function readAllXmlAndSave()
    $xml_files = glob(TMP . 'xml/*.xml');
    foreach($xml_files as $fileXml){
        $explStr = explode('/', $fileXml);
        $filename = $explStr[count($explStr) - 1];
        $path = TMP . '/xml/' . $filename;
        $file = new File($path, false);

        if($file->exists()){
           $string = $file->read();
           //some work
           $file->close();
           $file->delete();
        }
    }
}

I have create a simple script to understand how lock file works into cakephp 3 but seems that property lock doesn't work as I aspected.

code

$path = TMP . '/xml/test.xml'; //inside there is "HELLO"
$file = new File($path, false);

$string = $file->read();
echo($string);
$file->lock = true;

$string2 = $file->read();
echo($string2);

$string3 = $file->read();
echo($string3);

I aspected that only the first echo work not the other.. Why I get always:

HELLO
HELLO
HELLO 

and not only the first echo?

HELLO