PHP - Error Handling and Logging
These are functions dealing with error handling and logging. They allow us to define our own error handling rules, as well as modify the way the errors can be logged. This allows us to change and enhance error reporting to suit our needs.
With the logging functions, we can send messages directly to other machines, to an email, to system logs, etc., so we can selectively log and monitor the most important parts of your applications and websites.
The error reporting functions allow us to customize what level and kind of error feedback is given, ranging from simple notices to customized functions returned during errors.
Installation
There is no installation needed to use these functions. These functions are part of the PHP core.
Runtime Configuration
The behavior of these functions is affected by settings in php.ini. See Runtime Configuration.
PHP Error Handling and Logging Functions
| Functions | Description |
|---|---|
| debug_backtrace() | Generates a backtrace. |
| debug_print_backtrace() | Prints a backtrace. |
| error_clear_last() | Clears the most recent error. |
| error_get_last() | Gets the last occurred error |
| error_log() | Send an error message to the defined error handling routines. |
| error_reporting() | Sets which PHP errors are reported. |
| restore_error_handler() | Restores the previous error handler function. |
| restore_exception_handler() | Restores the previously defined exception handler function. |
| set_error_handler() | Generates a user-level error/warning/notice message. |
| set_exception_handler() | Sets a user-defined exception handler function. |
| trigger_error() | Sets a user-defined error handler function. |
| user_error() | Generates a user-level error/warning/notice message. Alias of trigger_error() function. |
PHP Errors and Logging Constants
The constants below are always available as part of the PHP core.
| Value | Constant | Type | Description |
|---|---|---|---|
| 1 | E_ERROR | Integer | Fatal run-time errors. These indicate errors that can not be recovered from, such as a memory allocation problem. Execution of the script is halted. |
| 2 | E_WARNING | Integer | Run-time warnings (non-fatal errors). Execution of the script is not halted. |
| 4 | E_PARSE | Integer | Compile-time parse errors. Parse errors should only be generated by the parser. |
| 8 | E_NOTICE | Integer | Run-time notices. Indicate that the script encountered something that could indicate an error, but could also happen in the normal course of running a script. |
| 16 | E_CORE_ERROR | Integer | Fatal errors that occur during PHP's initial startup. This is like an E_ERROR, except it is generated by the core of PHP. |
| 32 | E_CORE_WARNING | Integer | Warnings (non-fatal errors) that occur during PHP's initial startup. This is like an E_WARNING, except it is generated by the core of PHP. |
| 64 | E_COMPILE_ERROR | Integer | Fatal compile-time errors. This is like an E_ERROR, except it is generated by the Zend Scripting Engine. |
| 128 | E_COMPILE_WARNING | Integer | Compile-time warnings (non-fatal errors). This is like an E_WARNING, except it is generated by the Zend Scripting Engine. |
| 256 | E_USER_ERROR | Integer | User-generated error message. This is like an E_ERROR, except it is generated in PHP code by using the PHP function trigger_error(). |
| 512 | E_USER_WARNING | Integer | User-generated warning message. This is like an E_WARNING, except it is generated in PHP code by using the PHP function trigger_error(). |
| 1024 | E_USER_NOTICE | Integer | User-generated notice message. This is like an E_NOTICE, except it is generated in PHP code by using the PHP function trigger_error(). |
| 2048 | E_STRICT | Integer | Enable to have PHP suggest changes to your code which will ensure the best interoperability and forward compatibility of your code. |
| 4096 | E_RECOVERABLE_ERROR | Integer | Catchable fatal error. It indicates that a probably dangerous error occurred, but did not leave the Engine in an unstable state. If the error is not caught by a user defined handle (set by set_error_handler() function), the application aborts as it was an E_ERROR. |
| 8192 | E_DEPRECATED | Integer | Run-time notices. Enable this to receive warnings about code that will not work in future versions. |
| 16384 | E_USER_DEPRECATED | Integer | User-generated warning message. This is like an E_DEPRECATED, except it is generated in PHP code by using the PHP function trigger_error(). |
| 32767 | E_ALL | Integer | All errors, warnings, and notices. |
The above values (either numerical or symbolic) are used to build up a bitmask that specifies which errors to report. The bitwise operators can be used to combine these values or mask out certain types of errors.
