Description:
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other processes are denied to write the file while it is shared-locked, but attempting to do so prevents filesize() from working

Test script:
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<?php

// create a file of 6 bytes
$path = __DIR__ . "/foo.txt";
file_put_contents($path, "123456");


// (1)
// open that file for read and shared-lock it
$file = fopen($path, "r");
flock($file, LOCK_SH | LOCK_NB);


// (2)
// attempt to write that file concurrently while the lock is active
echo `php -r "file_put_contents('$path', 'baz');"`;
// this step fails as expected -- means the file is still "123456"


// (3)
// attempt to read the file's size
clearstatcache(FALSE, $path);
$fileSize = filesize($path);
// should return 6 bytes but returns 0


// (4)
// this fails as consequence
echo $fileSize . "\n";
echo fread($file, $fileSize);


flock($file, LOCK_UN);
fclose($file);

Expected result:
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should work as if the step (2) was commented out