Error and Exception Handling in PHP

Error and Exception Handling in PHP

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  Topic: Error andException Handling in PHP Error and Exception Handling in PHP
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  Contents • Error andError Handling • Using die() function • Defining Custom Error Handling Function • Error Parameter • Possible Error levels • Possible Error levels Exceptions Handling • Creating Custom Exception Handler Page 2 out of 10Error and Exception Handling in PHP
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  Error and ErrorHandling • An error is something you have done which is considered to be incorrect or wrong, or which should not have been done. • Error handling is the process of catching errors raised by our program and then taking appropriate action to prevent unforeseen consequences. Page 3 out of 10Error and Exception Handling in PHP
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  Using die() function Byusing die() function we can stop the process or jump to the next process if there is a error. Normally it is used when file is not found. Example: Page 4 out of 10 if(!file_exists("/tmp/test.txt")) { die("File not found"); } else { $file = fopen("/tmp/test.txt","r"); print "Opend file; } Error and Exception Handling in PHP
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  Defining Custom ErrorHandling Function • We can write our own function to handling any error. PHP provides us a framework to define error handling function. • This function must be able to handle minimum two parameters (error level and error message) but can accept up to five parameters (optionally: file, line- number, and the error context) Syntax: Error_Function_Name(Error_Level, Error_Message, Error_File, Error_Line, Error_Context) Page 5 out of 10Error and Exception Handling in PHP
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  Error Parameter There are5 kinds of error parameters • Error_level - A value number, specifies the error report level for the user-defined error. • Error_message - Message for the user-defined error • Error_file - File name in which the error occurred • Error_line - Line number in which the error occurred • Error_context - Array containing every variable and their values in use when the error occurred. Page 6 out of 10Error and Exception Handling in PHP
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  Possible Error levels •.E_ERROR - Fatal run-time errors • E_WARNING - Non-fatal run-time errors • E_PARSE - Compile-time parse errors • E_NOTICE - Run-time notices. • E_CORE_ERROR - Fatal errors that occur during PHP's initial start-up. • E_CORE_WARNING - Non-fatal run-time errors. This occurs during PHP's initial start-up. • E_USER_ERROR - Fatal user-generated error. • E_USER_WARNING - Non-fatal user-generated warning. • E_USER_NOTICE - User-generated notice. • E_ALL - All errors and warnings, except level E_STRICT Page 7 out of 10Error and Exception Handling in PHP
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  Exceptions Handling PHP 5has an exception model similar to that of other programming languages. Exceptions are important and provides a better control over error handling. • Try − A function using an exception should be in a "try" block. If the exception does not trigger, the code will continue as normal. However if the exception triggers, an exception is "thrown". • Throw − This is how you trigger an exception. Each "throw" must have at least one "catch". • Catch − A "catch" block retrieves an exception and creates an object containing the exception information. Page 8 out of 10Error and Exception Handling in PHP
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  Creating Custom ExceptionHandler We can define our own custom exception handler. By using following function to set a user-defined exception handler function. Syntax: string set_exception_handler ( callback $exception_handler ) Example: <?php function exception_handler($exception) { echo "Uncaught exception: " , $exception->getMessage(), "n"; } set_exception_handler('exception_handler'); throw new Exception('Uncaught Exception'); echo "Not Executedn"; ?> Page 9 out of 10Error and Exception Handling in PHP
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  Page 10 outof 10Error and Exception Handling in PHP