You already learned how PHP error handling works, what PHP errors are in their essence, and how to work with them. Still, there is a lot of functions you don't know. Some of them (like PHP display errors) may come in handy often.
PHP error handling is not a task you'd want to put away for long. Therefore, in this tutorial, we will introduce you with various functions and constants that will prove helpful to you as you're using PHP error handlers and creating custom error logs.
Contents
PHP Error: Main Tips
- PHP error functions are meant for dealing with error handling and logging tasks.
- Error functions allow you to define how PHP errors will be handled and logged.
- Logging errors means sending their messages to be saved in specified files, emails and other kind of system logs.
- Error report functions let you customize how certain PHP errors are reacted to, and the level of feedback.
- The functions are inbuilt into the PHP core.
- This tutorial explains in detail what is a PHP error.
Settings for Runtime Configuration
The way these functions behave is affected by the settings located in php.ini:
| Name | Default | Description | Changeable |
|---|---|---|---|
| error_reporting | NULL | Set PHP error reporting level (either integer or named constants) | PHP_INI_ALL |
| display_errors | "1" | Specify whether errors are to be printed to the screen, or if they would be hidden from the user. Note: NEVER use this setting on production systems (only to support your development) |
PHP_INI_ALL |
| display_startup_errors | "0" | Even if PHP display errors is on, errors which occur during PHP's startup sequence will not be displayed Note: Keeping display_startup_errors off is recommended, except when debugging |
PHP_INI_ALL |
| log_errors | "0" | Define which script error message should be logged to, the server error log or error_log. Note: It is strongly advised to use error logging instead of error displaying on production web sites |
PHP_INI_ALL |
| log_errors_max_len | "1024" | Used for setting maximum length of log_errors byte-wise. Value 0 can be used to apply no maximum length. This length is to apply to logged, displayed errors, as well as to $php_errormsg (implemented in PHP 4.3) | PHP_INI_ALL |
| ignore_repeated_errors | "0" | Specify whether to log repeating error messages. If set to 1 it will stop logging errors that repeating errors in the same file on the same line (implemented in PHP 4.3) | PHP_INI_ALL |
| ignore_repeated_source | "0" | Specify whether to log repeating error messages. If set to 1 it will stop logging errors with repeating errors from different files or source lines (implemented in PHP 4.3) | PHP_INI_ALL |
| report_memleaks | "1" | When set to 1 (default value), this parameter shows a report of memory leaks that have been detected by the Zend memory manager (implemented in PHP 4.3) | PHP_INI_ALL |
| track_errors | "0" | When set to 1, last error message always is present inside the variable $php_errormsg | PHP_INI_ALL |
| html_errors | "1" | Turn off HTML tags in error messages | PHP_INI_ALL PHP_INI_SYSTEM in PHP <= 4.2.3. |
| xmlrpc_errors | "0" | Turn off normal PHP error reporting and start formatting errors as XML-RPC error messages (implemented in PHP 4.1) | PHP_INI_SYSTEM |
| xmlrpc_error_number | "0" | Used as value of XML-RPC faultCode element (implemented in PHP 4.1) | PHP_INI_ALL |
| docref_root | "" | (implemented in PHP 4.3) | PHP_INI_ALL |
| docref_ext | "" | (implemented in PHP 4.3.2) | PHP_INI_ALL |
| error_prepend_string | NULL | Specify string to output before error message | PHP_INI_ALL |
| error_append_string | NULL | Specify string to output after error message | PHP_INI_ALL |
| error_log | NULL | Specify the name of file where script errors are to be logged. File should be set to be writable by web server's user. If special value syslog is used, errors are sent to system logger instead | PHP_INI_ALL |
List of Functions to Handle Errors
For the PHP error management, you are welcome to use the following functions. The table below indicates the most common methods that might be applied to get information on the latest errors, set different handler functions and perform other related actions:
| Function | Description |
|---|---|
| debug_backtrace() | Generate backtrace |
| debug_print_backtrace() | Print backtrace |
| error_get_last() | Return last error that occurred |
| error_log() | Send error message to log, to file, or to mail account |
| error_reporting() | Specify which errors are reported |
| restore_error_handler() | Restore previous PHP error handler |
| restore_exception_handler() | Restore previous exception handler |
| set_error_handler() | Set user-defined PHP error handler function |
| set_exception_handler() | Set user-defined exception handler function |
| trigger_error() | Create user-level error message |
| user_error() | Alias of trigger_error() function |
Relevant Predefined Constants
In PHP error handling, you can use the predefined constants that are designed for allowing you to set which errors are supposed to be displayed. Take a look at the following table and learn the meaning of each constant:
| Value | Constant | Description |
|---|---|---|
| 1 | E_ERROR | Fatal run-time error, which cannot be recovered from, halts script execution. |
| 2 | E_WARNING | Minor, non-fatal error, which occur while running the script and do not stop it. |
| 4 | E_PARSE | Compile-time errors, generated by the parser. |
| 8 | E_NOTICE | This include run-time notices, which could include minor errors as well as notices you may get when normally running the script. |
| 16 | E_CORE_ERROR | Fatal errors PHP startup error, much like E_ERROR, only that generated by PHP core. |
| 32 | E_CORE_WARNING | Non-fatal PHP startup errors, much like E_WARNING, only that generated by PHP core. |
| 64 | E_COMPILE_ERROR | Fatal errors. generated during compile-time, much like E_ERROR only that generated by Zend Scripting Engine. |
| 128 | E_COMPILE_WARNING | Non-fatal errors, generated during compile-time, much like E_WARNING only thatgenerated by Zend Scripting Engine. |
| 256 | E_USER_ERROR | Fatal error, user-generated error, a lot like E_ERROR only that they are set by code author using trigger_error() function. |
| 512 | E_USER_WARNING | Non-fatal user-generated warnings, a lot like E_WARNING only that they are set by code author using trigger_error() function. |
| 1024 | E_USER_NOTICE | Notice, user-generated, a lot like E_NOTICE only that they are set by code author using trigger_error() function. |
| 2048 | E_STRICT | Lets PHP suggest changes for your code that will ensure the most optimal interoperability and forward compatibility for your code (Since PHP 5 but only got included in E_ALL in PHP 5.4) |
| 4096 | E_RECOVERABLE_ERROR | Fatal error, which can be caught, a lot like E_ERROR , but it can be caught using a user-defined PHP error handler, that can be set up using set_error_handler(). |
| 8192 | E_DEPRECATED | All existing errors, warnings and notices (E_STRICT became a part of E_ALL in PHP version 5.4) |
| 16384 | E_USER_DEPRECATED | Warning message, generated by the user, much like E_DEPRECATED, only that it is generated in PHP code using PHP function trigger_error() (Since PHP 5.3) |
| 32767 | E_ALL | Enable every available PHP error and warning (except for E_STRICT in versions earlier than 5.4) |
PHP Error: Summary
- To handle and log errors, you should use special PHP error functions.
- When an error is logged, their messages are sent and saved in a log, such as a specified file or email.
- Using PHP error reporting, you can define system's feedback to particular PHP errors and its level.
- These functions don't require special installation.
- To remember what is a PHP error, visit this tutorial.