Error reporting in php

Error reporting in php

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  ERROR REPORTING BY: IQRABALOCH
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  What is error? •An error is a type of mistake. We can say an error is a condition of having incorrect or false knowledge or an error is defined as an unexpected, invalid program state from which it is impossible to recover. • Error can also be defined as “a deviation from accuracy or correctness”. A “mistake” is an error caused by fault: the fault being misjudgment, carelessness or forgetfulness. An error message with filename, like number and a message describing the error is sent to be the browser.
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  Types of error Thereare 12 unique error types, which can be grouped into 3 main categories: • Informational (Notices) • Actionable (Warnings) • Fatal (Runtime)
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  Informational Errors • Harmlessproblem, non-critical errors that PHP encounters while executing a script. In the notice error execution of the script does not stop. e.g. use of an undefined variable, defining a string without quotes, Referencing non-existent array keys etc.
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  Actionable Errors • Indicatethat something clearly wrong has happened and that action should be taken. e.g. file not present, database not available, missing function arguments, etc.
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  Fatal Errors • Somethingso terrible has happened during execution of your script that further processing simply cannot continue. e.g. parsing error, calling an undefined function, require() when the file does not exist etc.
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  Identifying Errors notice warning fatal
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  Enabling errors • display_errors= On • error_reporting = ~E_ALL
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  Customizing Error Handling •Generally, how PHP handles errors is defined by various constants in the installation (php.ini). • There are several things you can control in your scripts however..
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  1. Set errorreporting settings error_reporting($level) This function can be used to control which errors are displayed, and which are simply ignored. The effect only lasts for the duration of the execution of your script.
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  1. Set errorreporting settings <?php // Turn off all error reporting error_reporting(0); // Report simple running errors error_reporting(E_ERROR | E_WARNING | E_PARSE); // Reporting E_NOTICE can be good too (to report uninitialized // variables or catch variable name misspellings ...) error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE); // Report all errors except E_NOTICE error_reporting(E_ALL ^ E_NOTICE); // Report ALL PHP errors error_reporting(E_ALL); ?>
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  1. Set errorreporting settings • Hiding errors is NOT a solution to a problem. • It is useful, however, to hide any errors produced on a live server. • While developing and debugging code, displaying all errors is highly recommended!
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  2. Suppressing Errors •The special @ operator can be used to suppress function errors. • Any error produced by the function is suppressed and not displayed by PHP regardless of the error reporting setting.
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  2. Suppressing Errors •Error suppression is NOT a solution to a problem. • It can be useful to locally define your own error handling mechanisms. • If you suppress any errors, you must check for them yourself elsewhere.
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  3. Custom ErrorHandler • You can write your own function to handle PHP errors in any way you want. • You simply need to write a function with appropriate inputs, then register it in your script as the error handler. • Function called set_error_handler(), it allows to divert all PHP errors to a custom function that are defined, instead of sending them to the default handler.
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  3. Custom ErrorHandler • Custom function must be capable of accepting a minimum of two mandatory arguments: o Error type o Message • and up to three additional arguments: o File name o Line number o Context • These arguments are then used to create an error page that is friendlier and more informative than PHP's standard one-line error message
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  3. Custom ErrorHandler function err_handler( $errcode,$errmsg,$file,$lineno, $context) { echo ‘An error has occurred!<br />’; echo “file: $file<br />”; echo “line: $lineno<br />”; echo “Problem: $errmsg”; echo “Variable State: $contexts”; return true; }
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  3. Custom ErrorHandler • The function then needs to be registered as your custom error handler: set_error_handler(‘err_handler’); • You can ‘mask’ the custom error handler so it only receives certain types of error. e.g. to register a custom handler just for user triggered errors: set_error_handler(‘err_handler’, E_USER_NOTICE | E_USER_WARNING | E_USER_ERROR);
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  4. Pulling theTrigger • PHP allows you to use its built-in error handling system to raise your own custom errors as well. • This is accomplished via a function named trigger_error(), which allows you to raise any of the three error types reserved for users: E_USER_NOTICE, E_USER_WARNING and E_USER_ERROR. • When these errors are triggered, PHP's built-in handler will automatically wake up to handle them.
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  4. Pulling theTrigger $db = @mysql_connect($h,$u,$p); if (!$db) { trigger_error(‘blah’,E_USER_ERROR); }
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  Review • Various differenterror types exist in PHP. • The error handling system is highly flexible, and your own error handling methods can be developed.