PHP exception error handling mechanism and error handling (_php) tutorial

In PHP we use the most common error mechanism has try catch{} this to handle can be very instant noodles catch to error, but in PHP for a lot of also provide error view and error closed this can be processed in php.ini can also be in the file at the beginning of the Error_display (0 ), to not show errors

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$a = fopen (' test.txt ', ' R '); There is no judgment on the file opened, if the file does not exist will be an error ?>

Then the correct wording should be as follows:

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if (file_exists (' Test.txt ')) { $f =fopen (' Test.txt ', ' R '); Close when you are finished using Fclose ($f); } ?>

One, PHP error handling of three ways A, simple die () statement;
Equivalent to exit ();
Cases:

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if (!file_exists (' Aa.txt ')) { Die (' file does not exist '); } else { Perform actions } If the above die () is triggered, then ECHO is not executed here echo ' OK ';

Concise wording:

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File_exits (' aaa.txt ') or Die (' File not present '); echo ' OK ';

B, custom errors and error triggers

1, error processor (custom error, commonly used for syntax error handling)
Create a custom error function (processor) that must be capable of handling at least two parameters (Error_level and errormessage), but can accept up to five parameters (Error_file, Error_line, Error_context)
Grammar:

function Error_function ($error _level, $error _message, $error _file, $error _line, $error _context)
You will also need to overwrite Set_error_handler () when you create it;
Set_error_handler (' error_function ', e_warning);//Here error_function corresponds to the custom processor name created above, and the second parameter is the error level using the custom error handler;

Error Reporting level (learn it)

These error reporting levels are different types of errors that the error handler is designed to handle:

Value constant Description
2 e_warning non-fatal run-time error. Script execution is not paused.
8 E_notice run-time Notice.

The script discovers that an error may have occurred, but it may also occur when the script is running correctly.

The e_user_error fatal user-generated error. This is similar to the e_error that programmers use to set the PHP function Trigger_error ().
E_user_warning a non-fatal user-generated warning. This is similar to the e_warning that programmers use to set the PHP function Trigger_error ().
1024x768 E_user_notice user-generated notifications. This is similar to the e_notice that programmers use to set the PHP function Trigger_error ().
4096 E_recoverable_error A fatal error that can be captured. Similar to E_error, but can be captured by user-defined handlers. (see Set_error_handler ())
8191 E_all all errors and warnings except level e_strict.

(In PHP 6.0,e_strict is part of E_all)

2. Error trigger (typically used to handle logical errors)
Requirements: For example to receive an age, if the number is greater than 120, it is considered a mistake
Traditional methods:

if ($age >120) {
Echo ' age error '; exit ();
}

Using triggers:

if ($age >120) {
Trigger_error (' Error message ' [, ' Error level ']), where the error level is optional and is used to define the level of the error
User-defined levels include the following three types: E_user_warning, E_user_error, E_user_notice
Trigger_error (' age error ');//This is the default error handling of the system being called, we can also use the custom processor
}
Custom processor, same as above
function Myerror ($error _level, $error _message) {
Echo ' Error text ';
}
Also need to change the system default processing function
Set_error_handler (' Myerror ', e_user_warning);//with above, the first parameter is the name of the custom function, and the second is the error level "Here is usually the following three kinds of error levels: E_user_warning, E_user _error, E_user_notice "
You can now use the custom error-handling function with Trigger_error.

Exercises:

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Date_default_timezone_set (' PRC '); function Myerror ($error _level, $error _message) { $info = "Error number: $error _leveln"; $info. = "error message: $error _messagen"; $info. = ' Occurrence time: '. Date (' y-m-d h:i:s '); $filename = ' aa.txt '; if (! $fp =fopen ($filename, ' a ')) { ' Create file '. $filename. ' Failure '; } if (is_writeable ($filename)) { if (!fwrite ($FP, $info)) { Echo ' Write file failed '; } else { Echo ' has successfully logged error messages '; } Fclose ($FP); } else { echo ' file '. $filename. ' Not writable '; } Exit (); } Set_error_handler (' Myerror ', e_warning); $fp =fopen (' Aaa.txt ', ' R '); ?>

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