PHP RFC: Catchable "call to a member function of a non-object"

• Version: 0.8
• Date: 2014-04-26
• Author: Timm Friebe thekid@php.net
• Status: In Draft
• First Published at: https://wiki.php.net/rfc/catchable-call-to-member-of-non-object

One of the most common fatal errors in PHP is the “call to a member function of a non-object” type. This occurs whenever a method is called on anything other than an object (usually null), e.g.:

// ...when getAction() returns null:
$this->getAction()->invoke();

If you want to run PHP as a webserver itself, fatal errors are problematic. For a long story on why you would want to do that in the first place, see http://marcjschmidt.de/blog/2014/02/08/php-high-performance.html

This proposal's essence is to turns fatal errors generated from calls to methods on a non-object into E_RECOVERABLE_ERRORs.

set_error_handler(function($code, $message) {
  var_dump($code, $message);
});
 
$x= null;
var_dump($x->method());
echo "Alive\n";

The above produces the following output:

int(4096)
string(50) "Call to a member function method() on a non-object"
NULL
Alive

This behavior is consistent with how type hints work. Framework authors can turn this into exceptions if they wish.

The following error handler could be embedded into frameworks:

set_error_handler(function($code, $message) {
  if (0 === strncmp('Call', $message, 4)) {
    throw new BadMethodCallException($message);
  } else if (0 === strncmp('Argument', $message, 8)) {
    throw new InvalidArgumentException($message);
  } else {
    trigger_error($message, E_USER_ERROR);
  }
}, E_RECOVERABLE_ERROR);
 
$x= null;
try {
  $x->method();
} catch (BadMethodCallException $e) {
  echo "Caught expected ", $e->getMessage(), "!\n";
}
echo "Alive\n";

This proposal doesn't go as far as the controversial RFC RFC: Engine exceptions.

This RFC is backwards compatible with previous PHP releases.

There is no impact on any SAPI.

No impact.

No effect, before, the script terminated.

This RFC targets PHP 5.7 or PHP 6.0, whichever comes first.

This RFC modifies the PHP language behaviour and therefore requires a two-third majority of votes.

There is a pull request available over at GitHub which includes tests. Feedback welcome!

Ideas for future work include:

• Also allowing to catch and handle other fatal errors

• PHP Bugs 46601, 51882 and 51848- bugs which would be fixed by this
• PHP Bug 54195 - related, motivates necessity
• HHVM throws a BadMethodCallException in these situations