How to improve the theoretical base in programming?

Question

PHP

For a long time he worked in the field of site support on php. However, it so happened that I wanted to try my hand at developing applications. I tried to get a job, almost all employers (more precisely, technical directors) kept saying that I lacked theoretical knowledge in the field of programming. What do you think they mean. And the most important question: where to get this knowledge, can you recommend books? I am a self-taught programmer (python\php).

Answer 1

Artem, welcome!
I am far from being a programming guru, and also, by the way, a self-taught programmer, however, my life experience and common sense in a similar situation would dictate to me a slightly different approach to solving the issue.
1. The most obvious, simple and correct (provided that this issue is still relevant and pressing for you) is to contact these people again and clarify with them personally what kind of knowledge they are talking about. Like a tracing paper: "Good afternoon! My name is Artem, then I was at your interview, they refused me, citing a lack of theoretical knowledge. Could you help me with advice, what kind of knowledge do I lack? This information would help me buy them...." Well, something like this...
2.In the future, when such situations arise, ask such questions directly at the interview. Otherwise, then again there will be these "fortune-telling on the coffee grounds."
3. By what criteria are you going to choose a source of knowledge offered to you by the opinions of people, each of which is a unique mixture of age, knowledge and experience, and, accordingly, your own vision of the situation?
4. Learning for yourself, studying at a university, and learning for a specific job are two different things. You need a third, as far as I understand. To do this, you need to clearly understand what the employer needs. And there are two options for a good interview result - you were hired; you were not hired, but you know what exactly you still need to do (what you lacked) to get you hired.
Let's simulate the situation:
You have come for an interview. You were refused: "You do not have enough theoretical knowledge." You said " OK" and left. They asked a question on the Toaster, they offered you 15 answers - you need to learn such and such algorithms, such and such patterns, and so on ... You call the recruiter back, ask a question, and they answer you that you lack theoretical knowledge about data transfer protocols .. Well, for example ...
We need knowledge for ourselves, for general education, so to speak - experienced guys have already sketched out info for you.
Need knowledge for a specific job / employer - ask them personally what they need from you.
That is my point of view. Good luck!
PS A little humor, regarding knowledge, customers and tools for solving a specific problem.

Answer 2

university books on programming

Answer 3

Least:

• Algorithms and data structures
  
• The device of operating systems
  
• Basic network protocols
  

Answer 4

https://www.youtube.com/user/TPMGTU