Implementation of phpstorm View method

I would like to ask the gods, I in the phpstorm ctrl+ right click to enter a method, but this method is an empty method, where is his specific implementation? For example, the function str_replace:

Click on the method
clipboard.png
:

clipboard.png

but the method here is empty, so how does it implement the replacement function? Thank you!

Php
Mar.20,2021

  

github search php for source code

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b30768-2bcfe.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b30768-2bcfe.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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