The problem was :
calling the same script twice with the same url from the browser will thread via the same process and flock() function non-blocking working on the process layer causing the second script to wait
as example calling example.com/test.php twice will cause the two requests work on the same process wile appending any random variable will create separate process for each single request like
example.com/test.php?rand=1
example.com/test.php?rand=2
works great .