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PHP Arrays, Classes, Errors & Exceptions
- 1. PHP Arrays & Classes Developed by Mr.V.Sivakumar
- 2. PHP Arrays • In general, an array is a data structure that allows the programmer to collect a number of related elements together in a single variable. • Unlike most other programming languages, in PHP an array is actually an ordered map, which associates each value in the array with a key. • PHP array is not only like other languages arrays, but it is also like their vector, hash table, dictionary, and list collections.
- 7. superglobal arrays • PHP uses special predefined associative arrays called superglobal variables that allow the programmer to easily access HTTP headers, query string parameters. • They are called superglobal because these arrays are always in scope and always exist, ready for the programmer to access or modify them without having to use the global keyword.
- 9. Errors and Exceptions • A failure in any one of these systems will mean that the web application will no longer run successfully. • Types of errors ■ Expected errors ■ Warnings ■ Fatal errors • An expected error is an error that routinely occurs during an application. An error as a result of user inputs, for instance, entering letters when numbers were expected. • Users will leave fields blank, enter text when numbers were expected, type in too much or too little text, forget to click certain things.
- 10. Errors and Exceptions • Warnings, that generate a PHP warning message (which may or may not be displayed) but will not halt the execution of the page. For instance, calling a function without a required parameter will generate a warning but not stop execution. • Fatal errors, which are serious in that the execution of the page will terminate unless handled in some way. These should truly be exceptional and unexpected, such as a required input file being missing or a database table or field disappearing.
- 11. PHP Error reporting • There are three main error reporting flags: ■ error_reporting ■ display_errors ■ log_errors • The error_reporting setting specifies which type of errors are to be reported error_reporting = E_ALL / E_ERROR / E_WARNING • display_error setting specifies whether error messages should or should not be displayed in the browser. php.ini file: display_errors = Off • log_error setting specifies whether error messages should or should not be sent to the server error log log_errors = On
- 12. PHP Error and Exception handling • Two mechanisms for handling runtime errors: ■ procedural error handling ■ Object-Oriented exception handling • procedural approach to error handling, the programmer needs to explicitly test for error conditions after performing a task that might generate an error. If(condition){ some code here } else { } • When a runtime error occurs, PHP throws an exception. This exception can be caught and handled either by the function, class, or page that generated the exception or by the code that called the function or class using try{ condition} catch(Exception e) {}
- 13. PHP Error and Exception handling • Custom error and exception handlers • It should provide the developer with detailed information about the state of the application when the exception occurred, information about the exception, and when it happened. • It should hide any of those details from the regular end user, and user with a generic message such as “Sorry but there was a problem,” or “Sorry but the system is down for maintenance.” Function myException($Exception) { Our own exception message / Code here }
- 14. Source Reference: Randy Connolly, Ricardo Hoar, Fundamentals of Web Development, Pearson Thank you