Ask the old question: what is the code of PHP used to debug

New question: What does PHP code use to debug?
What tools do PHP code use to debug? Online has said Var_dump, but I do not understand how to use, there are any other easier way?

I am a novice, please be sure to answer the details. Thank you so much.

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1, look at the error log, but also the most direct
2. Compulsory interception of var_dump in the middle of script (); exit;
3. PHP Debug
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Echo/print_r/var_dump () is a common use for these few.

And then open the PHP error message function
------Solution--------------------
Always use
Echo '

';
Print_r ($var);
How did it break?
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Debugging?? Do not know what you use the development tools are beginners with Notepad, will be written out of the page to run, if not the results you want, you can do echo the simplest! And in general, the SQL statement will be wrong, then you echo the SQL to put the results in the database to run, to see where the error  
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