fix(parsers/php): repair the PHP call-graph builder (tag grammar, callbacks, new, scopes, imports)

[gadievron]

Several defects in parsers/php/call_graph_builder.py + function_extractor.py; before this the PHP call
graph was effectively empty (see #1).

1. Tag grammar: the call extractor re-parsed tag-stripped function bodies with ts_php.language_php() (the
   tag-REQUIRING grammar), which treats tagless input as inert text -- so ZERO call nodes were found and
   the entire PHP call graph was empty. Use language_php_only(). Foundational: every fix below only
   produces edges because of it.

2. Higher-order callbacks: call_user_func / call_user_func_array / array_map / array_filter / array_walk /
   array_reduce / usort / uasort / uksort / preg_replace_callback are in PHP_BUILTINS, so
   _resolve_function_call returned None before inspecting their callback argument. A CALLBACK_BUILTINS map
   now resolves the string-literal callback ('fn', 'Class::method', or ['Class','method']) at the builtin's
   callback position. The outer builtin call stays filtered; variable/closure callbacks have no static
   target.

3. use-import node type: _extract_imports matched use_declaration, but tree-sitter-php emits
   namespace_use_declaration, so use App\Service\Foo; imports were never recorded. Match the real node
   type; handle grouped use A, B; and strip as Alias.

4. Import-file matching: _resolve_simple_call matched import_name in file_path -- an unanchored substring
   -- so an import 'Bar' matched 'app/BarBaz/x.php'. Match the import file name (anchored: endswith the
   basename .php, or exact).

5. new/__construct: new Foo(...) parses as object_creation_expression, which the traversal never visited,
   so constructors were untracked. Add the node type + resolve the class __construct.

6. self/static/parent scopes: in tree-sitter-php self/static/parent are relative_scope nodes, not
   name, so _resolve_scoped_call never captured the scope and ALL self::/static::/parent:: calls were
   silently dropped. Handle relative_scope; resolve parent:: in the superclass (from the class's extends,
   namespace-stripped), with no fall-back to the caller's own class (which would mis-link an override's
   parent:: call to itself).

7. Case-insensitive builtins: _is_builtin compared case-sensitively, but PHP function names are
   case-insensitive, so e.g. CALL_USER_FUNC was not recognized. Compare name.lower().

Scope: PHP-specific (the c/python/ruby/zig/go call-graph builders are separate implementations).

Tests: tests/test_php_call_graph.py (new; the package had no php call-graph tests) -- loaded under a
unique importlib name (call_graph_builder/function_extractor are basenames shared by every parser). Eight
behavioral tests: tagless body produces edges, callback builtins resolve, new->__construct,
parent::->superclass, parent:: with a namespaced superclass, case-insensitive builtins, anchored import
match, namespace_use_declaration import. RED 8 failed (pre-fix) -> GREEN 8 passed; ruff clean; full suite
184 passed / 63 skipped.

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com

[gadievron]

Superseded by #134 (the 2026-06-24 release), which independently re-landed this parser work — the added code and tests are verified present on origin/master (line-by-line subset check). Closing to unclog the review queue; please reopen if a specific hunk is found missing on master.