Replacement Strings tutorial and PHP edu

I went over a tutorial on regex as I know that this is a needed part for a php edu. Is the Replacement Strings tutorial something that is needed too:

https://www.regular-expressions.info...etutorial.html

Is this something closely related to the PHP programming or not really (like can I find a use of that in the manual on php.net)? How closely would this be relevant / related / needed as far as php programming work (on a scale from 1 to 10, 1 - not needed, 10 - needed). I am planning on skipping this tutorial for now. I've been working on websites for 7+ years and I've never heard of this.