Support proper return value of DOMDocument::createElement, false almost never happens #13792
Description
Feature request
Currently, PHPStan infers benevolent union to prevent usability degradation while using this function. But this makes us unable to use checkBenevolentUnionTypes: true.
Luckily, the false can be statically eliminated by checking the argument passed (any valid name never returns false nor throw exception). I believe that most of the time, constant strings are used there.
Examples that Return FALSE:
$doc = new DOMDocument();
$doc->strictErrorChecking = false; // Critical: must be disabled
// All of these return FALSE:
$doc->createElement('123element'); // Starts with digit
$doc->createElement('my element'); // Contains space
$doc->createElement('my@element'); // Contains @ symbol
$doc->createElement(''); // Empty name
$doc->createElement('!element'); // Starts with !
$doc->createElement('elem&ent'); // Contains ampersand
$doc->createElement('.element'); // Starts with dot
$doc->createElement('-element'); // Starts with hyphenBehavior Modes:
| strictErrorChecking | Invalid Name Behavior | Valid Name Behavior |
|---|---|---|
| true (default) | Throws DOMException | Returns DOMElement |
| false | Returns FALSE + Warning | Returns DOMElement |
See real behaviour as proof. I also let Claude Code analyse php-src to verify this behaviour.
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