Solving Undefined Variables

Consider this example:

if (somethingIsTrue()) {
	$foo = true;
} elseif (orSomethingElseIsTrue()) {
	$foo = false;
} else {
	$this->redirect('homepage');
}

doFoo($foo); // possibly undefined variable $foo

Without any special knowledge we might think that the variable $foo might be undefined in case the else branch was executed. However, some specific method calls can be perceived by project developers also as early terminating - like a redirect() that stops execution by throwing an internal exception.

These methods can be configured by specifying a class on whose instance they are called using earlyTerminatingMethodCalls option key in the configuration file like this:

parameters:
	earlyTerminatingMethodCalls:
		Nette\Application\UI\Presenter:
			- redirect
			- redirectUrl
			- sendJson
			- sendResponse

The same applies to plain global functions. Early terminating functions can be defined using the earlyTerminatingFunctionCalls key, like this one with a global helper function redirect():

parameters:
	earlyTerminatingFunctionCalls:
		- redirect

PHPDoc tag @return never above a function or a method can be used instead of configuring earlyTerminatingFunctionCalls or earlyTerminatingMethodCalls.

Another issue you might encounter is that PHPStan doesn’t understand conditionally defined variables like this:

if ($foo) {
    $var = rand();
}

// 200 lines later:

if ($foo) {
    echo $var; // Variable $var might not be defined.
}

Fortunately this has been understood by PHPStan since version 0.12.64. So if you’re still experiencing this problem, make sure to upgrade to the latest version.

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