title: PHP how to use regular exp to inject a timestamp to the name of the file
body: <p>i have a debug file</p>
  
  <p>this file can be defined by admin system</p>
  
  <p>such as ../debug.log, or ../folder1/folder.log/file.txt or ..\folder1\yx.log</p>
  
  <p>how can i use regular exp to inject the timestamp to the file name for above string?</p>