It is possible to end the execution of a script with die and exit functions. They will interrupt the execution and destruct all resources.
<?php
if (mysql_connect('localhost', 'user', 'pass')) {
die('No database');
}
?>Exiting a script this way will also break any library that is including the die or exit. This may be difficult to spot, especially if those functions are used without any argument, thus displaying nothing about the location of the exit.
Exiting is also bad in a destructor : any call to exit and die in a destructor will prevent the other destructors to be executed.
It is usually better to throw an exception or raise an error (with trigger_error) or use any error handling set up available (returning a value, calling a error method, etc..).
The aim of this rule is to avoid using exit and die and rely on other error mechanisms.
This is considered a warning.
<?php
exit();
exit(23);
exit("an error message");
exit; // no parenthesis
die(__METHOD__);
?>This is considered legit.
<?php
// may be caught by error handler
trigger_error();
// may be caught by catch
throw new ExitException();
?>When the code is run as a commandline script, exit and die are good to return status, just like return.