I believe the benefits will include:
Tight database integration - Performance.
Security
Reduced network traffic
Precompiled (and originally compiled) code
Ability to create table triggers
Integration with SQL (less data type conversion, etc.)
In the end, although each approach and language will have advantages and disadvantages. Do not learn PL / SQL simply because you already know that PHP will be a loss to yourself personally and possibly from a career point of view. If you learn PL / SQL, how do you understand where it has advantages over PHP and where PHP has advantages over PL / SQL, but you will be in a better position to make a decision.
Good luck.
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