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PHP error handling

PHP error handling

Wrong classification:

Syntax error: The program cannot be run, and a syntax error is directly prompted

Runtime error: An error that occurs only when the program reaches a certain line or runs under certain circumstances.

Logic error: No error occurs (and prompts) when the program is run from beginning to end, but the calculation result of the program is wrong.

The main errors that programmers face and deal with are runtime errors.

Incorrect rating:

In PHP, various errors are divided into categories, and various errors are divided into about a dozen levels according to different serious programs and their sources (mechanisms).

Each level of error corresponds to an internal name - a system constant!

System error:

E_ERROR System serious error (once it occurs, the program stops executing immediately. This error is generally expected to be resolved immediately)

E_WARNING system warning (once it occurs, an error will be prompted and execution will continue. Usually the error is expected to be handled on the "next working day")

E_PARSE syntax error (Once it occurs, an error will be prompted and the code will not run at all - check the syntax before running.)

E_NOTICE system prompt (Once it occurs, an error will be prompted and the execution will continue. Send an email to notify and arrange time to solve it when you are free.)

What is their nature?

echo "
E_ERROR = ".E_ERROR;

echo "
E_WARNING = ".E_WARNING;

echo "
E_PARSE = ".E_PARSE;

echo "
E_NOTICE = ".E_NOTICE;

The output results are:

E_ERROR = 1

E_WARNING = 2

E_PARSE = 4

E_NOTICE = 8

It can be seen that they are just constants (integer constants) within the system; in fact, these constants (codenames) are just identifiers for us to "control" this type of error.

User-defined error:

There are only three:

E_USER_ERROR

E_USER_WARNING

E_USER_NOTICE

We can create (generate) errors ourselves in the program -- errors created to deal with unreasonable situations in certain data

For example: if you ask users to fill in their age, filling in 18 is OK, but filling in 188 is unreasonable -- there is no problem from a numerical perspective

Other errors:

E_ALL stands for all errors -- meaning it can "include" all errors.

E_STRICT stands for "strictness" syntax checking error - a certain syntax is executable, but is not welcome in the current PHP version.

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