feat(php): add Phpactor as alternative PHP language server

- Introduce PHP_PHPACTOR enum and integration in ls_config
- Implement PhpactorServer for PHP with dependency management
- Update docs and changelog for Phpactor support and usage
- Add project template entry for php_phpactor
- Provide tests for Phpactor LSP definition and reference features

test/solidlsp/php/test_php_phpactor.py

@@ -0,0 +1,111 @@
+from pathlib import Path
+
+import pytest
+
+from solidlsp import SolidLanguageServer
+from solidlsp.ls_config import Language
+
+
+@pytest.mark.php
+class TestPhpPhpactorLanguageServer:
+    @pytest.mark.parametrize("language_server", [Language.PHP_PHPACTOR], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.PHP], indirect=True)
+    def test_ls_is_running(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        """Test that the phpactor language server starts and stops successfully."""
+        assert language_server.is_running()
+        assert Path(language_server.language_server.repository_root_path).resolve() == repo_path.resolve()
+
+    @pytest.mark.parametrize("language_server", [Language.PHP_PHPACTOR], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.PHP], indirect=True)
+    def test_find_definition_within_file(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        # In index.php (0-indexed lines):
+        # Line 9: $greeting = greet($userName);
+        # Line 11: echo $greeting;
+        # Find the definition of $greeting from its usage on line 11 (0-indexed), char 6
+        definition_location_list = language_server.request_definition(str(repo_path / "index.php"), 11, 6)
+
+        assert definition_location_list, f"Expected non-empty definition_location_list but got {definition_location_list=}"
+        assert len(definition_location_list) >= 1
+        definition_location = definition_location_list[0]
+        assert definition_location["uri"].endswith("index.php")
+        assert definition_location["range"]["start"]["line"] == 9
+
+    @pytest.mark.parametrize("language_server", [Language.PHP_PHPACTOR], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.PHP], indirect=True)
+    def test_find_definition_across_files(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        # In index.php (0-indexed lines):
+        # Line 13: helperFunction();
+        # Find the definition of helperFunction which is in helper.php, line 2 (0-indexed)
+        definition_location_list = language_server.request_definition(str(repo_path / "index.php"), 13, 5)
+
+        assert definition_location_list, f"Expected non-empty definition_location_list but got {definition_location_list=}"
+        assert len(definition_location_list) >= 1
+        definition_location = definition_location_list[0]
+        assert definition_location["uri"].endswith("helper.php")
+        assert definition_location["range"]["start"]["line"] == 2
+
+    @pytest.mark.parametrize("language_server", [Language.PHP_PHPACTOR], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.PHP], indirect=True)
+    def test_find_definition_simple_variable(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        file_path = str(repo_path / "simple_var.php")
+
+        # In simple_var.php (0-indexed lines):
+        # Line 1: $localVar = "test";
+        # Line 2: echo $localVar;
+        # Find definition of $localVar from its usage on line 2, char 6
+        definition_location_list = language_server.request_definition(file_path, 2, 6)
+
+        assert definition_location_list, f"Expected non-empty definition_location_list but got {definition_location_list=}"
+        assert len(definition_location_list) >= 1
+        definition_location = definition_location_list[0]
+        assert definition_location["uri"].endswith("simple_var.php")
+        assert definition_location["range"]["start"]["line"] == 1
+
+    @pytest.mark.parametrize("language_server", [Language.PHP_PHPACTOR], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.PHP], indirect=True)
+    def test_find_references_within_file(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        index_php_path = str(repo_path / "index.php")
+
+        # In index.php (0-indexed lines):
+        # Line 9: $greeting = greet($userName);  // Definition of $greeting
+        # Line 11: echo $greeting;               // Usage of $greeting
+        # Find references for $greeting from its usage on line 11, char 6
+        references = language_server.request_references(index_php_path, 11, 6)
+
+        assert references, f"Expected non-empty references for $greeting but got {references=}"
+
+        actual_locations = [
+            {
+                "uri_suffix": loc["uri"].split("/")[-1],
+                "line": loc["range"]["start"]["line"],
+            }
+            for loc in references
+        ]
+
+        # Check that at least one reference points to $greeting usage in index.php
+        matching = [loc for loc in actual_locations if loc["uri_suffix"] == "index.php" and loc["line"] == 11]
+        assert matching, f"Expected reference to $greeting on line 11 of index.php, got {actual_locations}"
+
+    @pytest.mark.parametrize("language_server", [Language.PHP_PHPACTOR], indirect=True)
+    @pytest.mark.parametrize("repo_path", [Language.PHP], indirect=True)
+    def test_find_references_across_files(self, language_server: SolidLanguageServer, repo_path: Path) -> None:
+        helper_php_path = str(repo_path / "helper.php")
+
+        # Find references for helperFunction from its definition in helper.php
+        # Line 2 (0-indexed): function helperFunction(): void {
+        references = language_server.request_references(helper_php_path, 2, len("function "))
+
+        assert references, f"Expected non-empty references for helperFunction but got {references=}"
+
+        actual_locations_comparable = []
+        for loc in references:
+            actual_locations_comparable.append(
+                {
+                    "uri_suffix": loc["uri"].split("/")[-1],
+                    "line": loc["range"]["start"]["line"],
+                }
+            )
+
+        # Check that helperFunction usage in index.php line 13 is found
+        matching = [loc for loc in actual_locations_comparable if loc["uri_suffix"] == "index.php" and loc["line"] == 13]
+        assert matching, f"Usage of helperFunction in index.php (line 13) not found in {actual_locations_comparable}"