[b84330808]

This change and the description below were written by an LLM (Claude Code).

PHP_FUNCTION(implode) accepts an array as the first argument when the second is null, which is the same as implode($array), and the stub allows it (string|array $separator, ?array $array = null). The frameless variant that direct two-argument calls compile to parses argument 1 as a string unconditionally, so whether the call works depends on how it's made:

$a = ['a', 'b'];
implode($a, null);                    // TypeError: implode(): Argument #1 ($separator) must be of type string, array given
call_user_func('implode', $a, null);  // "ab"
join($a, null);                       // "ab" (the alias isn't frameless)

implode($a, 'x') also blames argument 1, while the regular function reports Argument #2 ($array) must be of type ?array, string given.

The fix handles an array first argument the way the regular function does.

The new phpt fails without the fix. It passes with it, also under opcache with function and tracing JIT, along with ext/standard/tests/strings and Zend/tests/frameless*.

This is a regression in 8.4, where frameless calls were introduced. 8.3 only has the regular function, which accepts this call. Targeting PHP-8.4. The diff also applies to master.