and, or, & xor logical operators aren't checked against variable-setting

[sybrew]

Code speaks a thousand words. Replace and with the other logical operators (or, xor), and the same error will yield.

$get_something_and_do_stuff = true;

$get_something_and_do_stuff
	and $something = get_something()
	and $something === 'something' // VariableAnalysis.CodeAnalysis.VariableAnalysis.UndefinedVariable
	and do_stuff();

Variable $something is undefined.
(VariableAnalysis.CodeAnalysis.VariableAnalysis.UndefinedVariable)

This is tricky, however, because the logical operators may prevent or bypass assigning variables; especially when the or-operator is used in sequence.

[sirbrillig]

Oh, interesting. I hadn't considered a single statement with multiple expressions that define and use a variable. Good find.

[sybrew]

I don't think it's feasible to create a fix for this, however. Consider these scenarios, where every instance of true/false may be a function or variable call which you can't test.

Positives:

false
	and $something = true
	or  'value' === $something; // warning

true
	and $something = true
	or 'value' === $something; // warning, never runs.

false
	or $something = false
	and 'value' === $something; // warning, never runs.

---

False positives:

false
	or $something = true
	and 'value' === $something; // warning that's incorrect

---

False negatives:

false
	and $something = true;

if ( $something ) { // no warning, but it's undefined...
	return false;
}