feat(extract): support PHP closures (#3409)

The bug:
PHP closures (`anonymous_function_creation_expression` and `arrow_function`)
were invisible to the graph, disconnecting API routes and callbacks from
the backend code.

The fix:
- Added closure syntax node types to _PHP_CONFIG's `function_types`.
- Updated engine.py to synthesize line-bound names (e.g., `{closure@42}`)
  for unnamed closures matching these AST node types, enabling them to be
  extracted as linkable nodes in the graph without ID collisions.

graphify/extract.py

@@ -1023,7 +1023,7 @@ _PHP_CONFIG = LanguageConfig(
         "enum_declaration",
         "trait_declaration",
     }),
-    function_types=frozenset({"function_definition", "method_declaration"}),
+    function_types=frozenset({"function_definition", "method_declaration", "anonymous_function_creation_expression", "arrow_function"}),
     import_types=frozenset({"namespace_use_clause"}),
     # object_creation_expression joins the dispatch set so `new Foo(...)` links
     # the constructing method to Foo (engine has a dedicated PHP branch: the
@@ -1041,7 +1041,7 @@ _PHP_CONFIG = LanguageConfig(
     # enums wrap their members in an enum_declaration_list rather than a
     # declaration_list, so the body walk needs it to reach enum methods/cases.
     body_fallback_child_types=("declaration_list", "compound_statement", "enum_declaration_list"),
-    function_boundary_types=frozenset({"function_definition", "method_declaration"}),
+    function_boundary_types=frozenset({"function_definition", "method_declaration", "anonymous_function_creation_expression", "arrow_function"}),
     import_handler=_import_php,
 )
 

graphify/extractors/engine.py

@@ -4415,7 +4415,10 @@ def _extract_generic(
                 func_name = _read_text(name_node, source) if name_node else None
 
             if not func_name:
-                return
+                if t in ("anonymous_function_creation_expression", "arrow_function"):
+                    func_name = f"{{closure@{node.start_point[0] + 1}}}"
+                else:
+                    return
             sanitized_name = (
                 config.sanitize_symbol_name_fn(func_name)
                 if config.sanitize_symbol_name_fn is not None

tests/test_extract_php_closures.py

@@ -0,0 +1,33 @@
+from pathlib import Path
+from graphify.extract import extract_php
+import pytest
+
+def test_php_closures(tmp_path):
+    src = b'''<?php
+$app->get('/api', function() {
+    return 1;
+});
+$fn = fn($x) => $x + 1;
+'''
+    php_file = tmp_path / 'dummy.php'
+    php_file.write_bytes(src)
+    
+    res = extract_php(php_file)
+    if res.get('error'):
+        pytest.skip(res['error'])
+        
+    nodes = {n['id']: n for n in res['nodes']}
+    labels = {n['label']: n for n in res['nodes']}
+    
+    # Assert closures are correctly generated
+    assert '{closure@2}()' in labels, "Missing anonymous_function_creation_expression node"
+    assert '{closure@5}()' in labels, "Missing arrow_function node"
+    
+    closure_1 = labels['{closure@2}()']
+    closure_2 = labels['{closure@5}()']
+    
+    # Check edges
+    edges = res['edges']
+    assert any(e['source'] == 'dummy.php' and e['target'] == closure_1['id'] and e['relation'] == 'contains' for e in edges), "Missing contains edge for closure_1"
+    assert any(e['source'] == 'dummy.php' and e['target'] == closure_2['id'] and e['relation'] == 'contains' for e in edges), "Missing contains edge for closure_2"
+