Here's a breakdown of what's happening in your script:
1) Your code is stuck in an infinite loop with while(true), preventing it from reaching the fclose() statement.
2) I ran tests with both File1.php and file2.php on my local server. While File1.php kept looping, file2.php immediately showed a "file is locked" message (indicating correct locking). Both files failed the lock test when refreshed afterward.
If you're using PHP > 5.3.2, remember that manual unlocking is required now:
The automatic unlocking upon closing a file handle was removed. Unlocking must now be done manually.
Source
For older PHP versions, the file will unlock once the script finishes executing. Since your script endlessly loops, it never truly finishes, hence keeping the file locked.
Even if you stop the script in your browser, the php-cgi.exe process linked to that script remains active until manually terminated via task manager (I confirmed this).
Solution:
1)
To resolve this issue and ensure proper file locking, remove the infinite loop to allow the script to gracefully end:
Use this revised script to lock the file for 30 seconds (loop removed):
<?php
$x = fopen("/var/www/abc.txt", "w");
if (flock($x, LOCK_EX|LOCK_NB)) {
print "No issues, I've acquired the lock, now waiting.";
sleep(30);
fclose($x); // Always close even pre-PHP 5.3.2
}
else {
print "Lock couldn't be obtained. Exiting. Good night.";
}
?>
2) On Linux machines, utilize LOCK_NB flag to verify file locking status. Add LOCK_NB for checking file lock like so:
while ( ! flock($f, LOCK_NB) )
{
sleep(1);
}
This forces the script to check for the lock every second, waiting for the other script to complete.
3) Utilize flock($fp, LOCK_UN) to explicitly release the lock instead of fclose();
In essence, your code should resemble this:
<?php
$x = fopen("/var/www/abc.txt", "w");
while(!flock($x,LOCK_NB)
sleep(1);
if (flock($x, LOCK_EX,true)) {
print "No problems, I got the lock, now I'm going to sit on it.";
sleep(30);
fflush($fp); // flush output before releasing the lock
flock($fp, LOCK_UN); // release the lock
} else {
print "Didn't quite get the lock. Quitting now. Good night.";
}
fclose($x);
?>