PEAR Manual - PEAR::raiseError()

Parameter

string $message: Error message. The default message is "unknown error" if left blank.
integer $code: Error code. It is recommended to use an error code for even the simplest errors, in order to simplify error handling and processing.
integer $mode: Error mode. This is one of PEAR_ERROR_RETURN, PEAR_ERROR_PRINT, PEAR_ERROR_TRIGGER, PEAR_ERROR_DIE, PEAR_ERROR_CALLBACK, or PEAR_ERROR_EXCEPTION. See setErrorHandling() for detailed information and examples of the meaning of these constants.
mixed $options: Error options. This depends on the value of $mode, and is documented in setErrorHandling().
mixed $userinfo: Optional user information. This can be used to store any error-specific information, and has an unspecified format.
string $error_class: Error class name to use as the error object. The default error class is PEAR_Error. Use this parameter to specify another class to use, such as a custom class extending PEAR_Error
boolean $skipmsg: Use this parameter if you are using a custom class that does not accept an error message in its constructor. Never use this parameter without the $error_class parameter - it will not work.