Handling error & exception in php

Handling Error & Exception in PHP
Presenter: Pravasini Sahoo, Mindfire Solutions
Date: 16/07/2015 1

Working as a PHP developer in MFS for more than 5 years.
My skill is on PHP, MySQL, HTML, HTML5, CSS, CSS3, jQuery, AJAX, Javascript, XML, ZendFramework, Goog
Zend Certified Engineer (ZCE) - Zend PHP 5.3 Certification
Oracle Certified Professional - OCP MySQL 5 Developer - Part 1 - 1Z0-871
Microsoft Certified Professional - MCP - Programming in HTML5 with Javascript & CSS3
Best Web Dev Article for month of January in CodeProject
Speaker in GDG group (Srusti Academy of Management, Koustuv Group)
Speaker in MSDC group (USBM)
Speaker in GDG group (IIT Bhubaneswar on HTML5 & CSS3)
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What are Errors
Types of PHP Errors
Ways to handle PHP Errors
What are Exceptions
Handling Exceptions
Default Exception handler
Conclusion
Questions!!!
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An Error is a term used to describe any issue that arises
unexpectedly that cause a computer to not function
properly.
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These are errors in which the code behaves unexpectedly due to
some code in the program not acting as expected.
Can use newrelic for finding and fixing problems in the server -
https://docs.newrelic.com/docs/agents/php-
agent/installation/php-agent-installation-ubuntu-debian
Sentry : It is very useful for logging the errors/exceptions
without writing the code manually. It will group the same error
messages and will be logged in a nice manner -
https://www.getsentry.com/welcome/

E_ERROR
E_WARNING
E_NOTICE
E_USER_ERROR
E_USER_WARNING
E_USER_NOTICE
E_RECOVERABLE_ERROR
E_ALL
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In general, these kind of errors can not be recoverable and it halts the
execution of the running script.
undefinedFunction();
#Fatal error: Call to undefined function undefinedFunction() in /test-
project/test.php on line 1
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Generally, these errors are non-fatal runtime errors and can be
recoverable. It does not halt the execution and also it indicates the
system/user that some problem has happened.
include(“missing-file.php”);
#Warning: include(file.php): failed to open stream: No such file or directory
in /test-project/test.php on line 1
#Warning: include(): Failed opening 'file.php' for inclusion
(include_path='.:') in /test-project/test.php on line 1
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These type of error produces notices in run-time context. Generally, it
happens when the script found something wrong which can show error while
running the script.
$a = $b + 1;
#Notice: Undefined variable: b in /test-project/test.php on line 1
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These are like E_ERROR but set by the user programmatically using
trigger_error().
if (function_exists(undefinedFunction)) {
undefinedFunction();
} else {
trigger_error('The function you called, does not exists',
E_USER_ERROR);
}
#Notice: Use of undefined constant undefinedFunction - assumed
'undefinedFunction' in /test-project/test.php on line 1
#Fatal error: The function you called, does not exists in /test-
project/test.php on line 4
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These are like E_WARNING but set by the user programmatically using
trigger_error().
if (include("file.php")) {
include("file.php");
} else {
trigger_error('The file you are searching for not found',
E_USER_WARNING);
}
#Warning: include(file.php): failed to open stream: No such file or directory
in /test-project/test.php on line 1
#Warning: include(): Failed opening 'file.php' for inclusion
(include_path='.:') in /test-project/test.php on line 1
#Warning: The file you are searching for not found in /test-project/test.php
on line 4
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These are like E_NOTICE but set by the user programmatically using
trigger_error().
if (isset($b)) {
$a = $b + 1;
} else {
trigger_error('$b is not defined yet');
}
#Notice: $b is not defined yet in /test-project/test.php on line 4
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Show the errors to users
Log the errors
Ignore them, as like nothing has happened
Act on them and fix it
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display_errors = on/1 in php.ini file
ini_set(‘display_errors’,1); in application config file
php_value display_errors 1 in .htaccess file
Set error_reporting() to the appropriate severity level
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log_errors = On in php.ini file
error_log = path/to/file in php.ini file
error_log(‘User Defined Error’); in your application
Send the errors through email
Log the errors in DB
Log into physical file structure
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Suppress Errors using @ operator
Like @fopen or @file_get_contents
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Using set_error_handler(<user_defined_error_handler>)
It has 5 parameters, which is used to get proper error
message
error_level
error_message
error_file
error_line
error_context
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In general, exception is a certain thing which is excluded from a general
statement or does not follow the rule.
In computer language, Exception handling is the process of responding to
the occurrence, during computation, often changing the normal flow of
program execution.
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try —> Try to run the code which may throw exception
throw —> Triggering an exception
catch —> Handle the thrown exception
finally —> Default code block to run, even after exception
Not available in PHP
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user-defined Exception Handler
It handles any uncaught exception
After handling, the script halts
function defaultExceptionHandler() {
// code to handle exception
}
set_exception_handler(‘defaultExceptionHandler’);
class CustomExceptionHandler() {
public function handleException() {
// code to handle exception
}
}
set_exception handler(array(‘CustomExceptionHandler’,
‘handleException’));
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Error or Exceptions are usual in PHP
Logging is very important
Do not ignore the errors
If not handled properly, they will turn into bugs
Always have a default error handler to log the errors and
handle in an efficient way, even if we know our code will
never show any error :)
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http://www.computerhope.com/jargon/e/error.htm
http://www.w3schools.com/php/php_exception.asp
http://www.informit.com/articles/article.aspx
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https://www.facebook.com/pravasini.sahoo.9
http://in.linkedin.com/pub/pravasini-sahoo/22/a4a/80
https://twitter.com/pravasinisahoo
Presenter: Pravasini Sahoo, Mindfire SolutionsPresenter: Pravasini Sahoo, Mindfire Solutions
https://plus.google.com/116915409923931471434/
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Handling error & exception in php

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