There are several types of errors and warnings in PHP. They are:
Table 15-1. PHP error types
| Value | Constant | Description | Note |
|---|---|---|---|
| 1 | E_ERROR | fatal run-time errors | |
| 2 | E_WARNING | run-time warnings (non fatal errors) | |
| 4 | E_PARSE | compile-time parse errors | |
| 8 | E_NOTICE | run-time notices (less serious than warnings) | |
| 16 | E_CORE_ERROR | fatal errors that occur during PHP's initial startup | PHP 4 only |
| 32 | E_CORE_WARNING | warnings (non fatal errors) that occur during PHP's initial startup | PHP 4 only |
| 64 | E_COMPILE_ERROR | fatal compile-time errors | PHP 4 only |
| 128 | E_COMPILE_WARNING | compile-time warnings (non fatal errors) | PHP 4 only |
| 256 | E_USER_ERROR | user-generated error message | PHP 4 only |
| 512 | E_USER_WARNING | user-generated warning message | PHP 4 only |
| 1024 | E_USER_NOTICE | user-generated notice message | PHP 4 only |
| E_ALL | all of the above, as supported |
The above values (either numerical or symbolic) are used to build up a bitmask that specifies which errors to report. You can use the bitwise operators to combine these values or mask out certain types of errors. Note that only '|', '~', '!', and '&' will be understood within php.ini, however, and that no bitwise operators will be understood within php3.ini.
In PHP 4, the default error_reporting setting is E_ALL & ~E_NOTICE, meaning to display all errors and warnings which are not E_NOTICE-level. In PHP 3, the default setting is (E_ERROR | E_WARNING | E_PARSE), meaning the same thing. Note, however, that since constants are not supported in PHP 3's php3.ini, the error_reporting setting there must be numeric; hence, it is 7.
The initial setting can be changed in the ini file with the error_reporting directive, in your Apache httpd.conf file with the php_error_reporting (php3_error_reporting for PHP 3) directive, and lastly it may be set at runtime within a script by using the error_reporting() function.
| Warning |
When upgrading code or servers from PHP 3 to PHP 4 you should check these settings and calls to error_reporting() or you might disable reporting the new error types, especially E_COMPILE_ERROR. This may lead to empty documents without any feedback of what happened or where to look for the problem. |
All PHP expressions can also be called with the "@" prefix, which turns off error reporting for that particular expression. If an error occurred during such an expression and the track_errors feature is enabled, you can find the error message in the global variable $php_errormsg.
| Warning |
Currently the @ error-control operator prefix will even disable error reporting for critical errors that will terminate script execution. Among other things, this means that if you use @ to suppress errors from a certain function and either it isn't available or has been mistyped, the script will die right there with no indication as to why. |