Also be careful when you say, “Web Development (PHP).”   PHP is not the only language used for creating web-sites, and in fact I think that it is a rather inferior choice.   Today it is possible to create many web sites without writing any source-code at all.   Furthermore, much of the time you will be being asked to work on an existing site, not a new one, and it’s anybody’s guess what technique might have been used at the time.

Always try to glean programming knowledge in context.   Look at how several different languages (and rapid-builder tools) do the same thing, and be sure that you are not looking just at books which described how it was done when the web (and PHP) was new.   There’s a lot of “prior art” out there now, that’s being used much more commonly than starting from ground zero.   You will find quite a few web-sites on places like GitHub ... places where the complete source-code of a site constructed in this-or-that can be found ... and study them.   Deconstruct them.   You’ll be doing a lot of “deconstructing the inner workings of existing code, so that you may enhance it and/or fix it” on the job.