Description:
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Re bug #47796:

Documentation for preg_replace only suggests to check PHP's string 
syntax in non-alarming way.
 
Given that replacement code with double quotes (which is even used in 
manual itself) could enable remote code execution, there should be a 
clearly worded and highlighted warning about this.

The fragment "This is done to ensure that no syntax errors arise from 
backreference usage with either single or double quotes" could lead 
readers to believe that PHP escapes strings thoroughly and properly.
That is not the case:

preg_replace('/.*/e','"$0"', '{$foo[}');


Expected result:
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Huge red box in manual with "Don't use /e".