Block cloning not working for fairly big file

[Herz3h]

Describe the Bug

With a docx file of roughly 5 pages (has full text on each page, with different styles)

Steps to Reproduce

Clone any block of a fairly big file (mine has 5 pages)

Expected Behavior

Blocks to be cloned

Current Behavior

Does not clone any block

Context

pcre.backtrack_limit | "1000000"
pcre.recursion_limit | "100000"
pcre.jit | "1"

• PHP Version: 7.12
• PHPWord Version: 0.13.*

The regex used (https://github.com/PHPOffice/PHPWord/blob/develop/src/PhpWord/TemplateProcessor.php#L739) has catastrophic backtracking when I try it on regex101.com and the only way to get this to work is to increase limit as following in my case:

ini_set("pcre.backtrack_limit", "23001337");
ini_set("pcre.recursion_limit", "23001337");

I tried optimizing the regex, but couldn't achieve much. I'm just reporting issue here for information since in my case I just increase the backtracking limit. But it may be something good to optimize ;)