(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)
trigger_error — Generates a user-level error/warning/notice message
$message, int $error_level = E_USER_NOTICE): boolUsed to trigger a user error condition, it can be used in conjunction with the built-in error handler, or with a user defined function that has been set as the new error handler (set_error_handler()).
This function is useful when you need to generate a particular response to an exception at runtime.
messageThe designated error message for this error. It's limited to 1024 bytes in length. Any additional characters beyond 1024 bytes will be truncated.
error_level
       The designated error type for this error. It only works with the E_USER
       family of constants, and will default to E_USER_NOTICE.
      
   This function returns false if wrong error_level is
   specified, true otherwise.
  
Example #1 trigger_error() example
See set_error_handler() for a more extensive example.
<?php
if ($divisor == 0) {
    trigger_error("Cannot divide by zero", E_USER_ERROR);
}
?>
     HTML entities in message are not
     escaped. Use htmlentities() on the message if
     the error is to be displayed in a browser.