How to fully understand the source code and other people write codes

How can we fully understand the source code and other people write codes
In addition to more output, read the function of not a function, and then through debugging to run in series, but also how to read the source code and other people wrote?

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English should be standard. Then combine the actual application scenario of the program to see what business logic is dealing with. increase, delete, change and search.
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First, the foundation is deep. To be able to read the code.

Second you can run it first. Look at the code based on business logic. Echo/var_dump debugging at any time. Do not understand the Internet to check.
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First use, know the specific file, folder function. Then master the basic operating flow. Then slowly a little change, analysis. You'll see more slowly. Know a lot.
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Proficient at least one programming language to understand PHP syntax
Do not have the framework of the general can understand, or the use of tools or forums to understand slowly.
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Use the manual first, then try it.
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First of all have to have the basis, what function to do what use to understand, followed by demand, then is the analysis code, analysis of the time according to the boss of the Department of Millet guidance: "Along with the author's ideas" All the way down. Like you want to see the structure of a building you have to understand the material, size, endurance ...

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