feat(php): add PHP/PSR-4 import resolution with composer.json support

- Add .php, .phtml to EXTENSIONS array
- Add ComposerConfig interface and loadComposerConfig() (mirrors TsconfigPaths pattern)
- Add resolvePhpImport() with PSR-4 longest-match resolution + suffix fallback
- Wire PHP handling into processImports() and processImportsFromExtracted()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gitnexus/src/core/ingestion/import-processor.ts

@@ -101,6 +101,37 @@ async function loadGoModulePath(repoRoot: string): Promise<GoModuleConfig | null
   return null;
 }
 
+/** PHP Composer PSR-4 autoload config */
+interface ComposerConfig {
+  /** Map of namespace prefix -> directory (e.g., "App\\" -> "app/") */
+  psr4: Map<string, string>;
+}
+
+async function loadComposerConfig(repoRoot: string): Promise<ComposerConfig | null> {
+  try {
+    const composerPath = path.join(repoRoot, 'composer.json');
+    const raw = await fs.readFile(composerPath, 'utf-8');
+    const composer = JSON.parse(raw);
+    const psr4Raw = composer.autoload?.['psr-4'] ?? {};
+    const psr4Dev = composer['autoload-dev']?.['psr-4'] ?? {};
+    const merged = { ...psr4Raw, ...psr4Dev };
+
+    const psr4 = new Map<string, string>();
+    for (const [ns, dir] of Object.entries(merged)) {
+      const nsNorm = (ns as string).replace(/\\+$/, '');
+      const dirNorm = (dir as string).replace(/\\/g, '/').replace(/\/+$/, '');
+      psr4.set(nsNorm, dirNorm);
+    }
+
+    if (isDev) {
+      console.log(`📦 Loaded ${psr4.size} PSR-4 mappings from composer.json`);
+    }
+    return { psr4 };
+  } catch {
+    return null;
+  }
+}
+
 // ============================================================================
 // IMPORT PATH RESOLUTION
 // ============================================================================
@@ -122,6 +153,8 @@ const EXTENSIONS = [
   '.go',
   // Rust
   '.rs', '/mod.rs',
+  // PHP
+  '.php', '.phtml',
 ];
 
 /**
@@ -551,6 +584,48 @@ function resolveGoPackage(
   return matches;
 }
 
+// ============================================================================
+// PHP PSR-4 IMPORT RESOLUTION
+// ============================================================================
+
+/**
+ * Resolve a PHP use-statement import path using PSR-4 mappings.
+ * e.g. "App\Http\Controllers\UserController" -> "app/Http/Controllers/UserController.php"
+ */
+function resolvePhpImport(
+  importPath: string,
+  composerConfig: ComposerConfig | null,
+  allFiles: Set<string>,
+  normalizedFileList: string[],
+  allFileList: string[],
+  index?: SuffixIndex,
+): string | null {
+  // Normalize: replace backslashes with forward slashes
+  const normalized = importPath.replace(/\\/g, '/');
+
+  // Try PSR-4 resolution if composer.json was found
+  if (composerConfig) {
+    // Sort namespaces by length descending (longest match wins)
+    const sorted = [...composerConfig.psr4.entries()].sort((a, b) => b[0].length - a[0].length);
+    for (const [nsPrefix, dirPrefix] of sorted) {
+      const nsPrefixSlash = nsPrefix.replace(/\\/g, '/');
+      if (normalized.startsWith(nsPrefixSlash + '/') || normalized === nsPrefixSlash) {
+        const remainder = normalized.slice(nsPrefixSlash.length).replace(/^\//, '');
+        const filePath = dirPrefix + (remainder ? '/' + remainder : '') + '.php';
+        if (allFiles.has(filePath)) return filePath;
+        if (index) {
+          const result = index.getInsensitive(filePath);
+          if (result) return result;
+        }
+      }
+    }
+  }
+
+  // Fallback: suffix matching (works without composer.json)
+  const pathParts = normalized.split('/').filter(Boolean);
+  return suffixResolve(pathParts, normalizedFileList, allFileList, index);
+}
+
 // ============================================================================
 // MAIN IMPORT PROCESSOR
 // ============================================================================
@@ -581,6 +656,7 @@ export const processImports = async (
   const effectiveRoot = repoRoot || '';
   const tsconfigPaths = await loadTsconfigPaths(effectiveRoot);
   const goModule = await loadGoModulePath(effectiveRoot);
+  const composerConfig = await loadComposerConfig(effectiveRoot);
 
   // Helper: add an IMPORTS edge + update import map
   const addImportEdge = (filePath: string, resolvedPath: string) => {
@@ -705,6 +781,15 @@ export const processImports = async (
           // Fall through if no files found (package might be external)
         }
 
+        // ---- PHP: handle namespace-based imports (use statements) ----
+        if (language === SupportedLanguages.PHP) {
+          const resolved = resolvePhpImport(rawImportPath, composerConfig, allFilePaths, normalizedFileList, allFileList, index);
+          if (resolved) {
+            addImportEdge(file.path, resolved);
+          }
+          return;
+        }
+
         // ---- Standard single-file resolution ----
         const resolvedPath = resolveImportPath(
           file.path,
@@ -757,6 +842,7 @@ export const processImportsFromExtracted = async (
   const effectiveRoot = repoRoot || '';
   const tsconfigPaths = await loadTsconfigPaths(effectiveRoot);
   const goModule = await loadGoModulePath(effectiveRoot);
+  const composerConfig = await loadComposerConfig(effectiveRoot);
 
   const addImportEdge = (filePath: string, resolvedPath: string) => {
     const sourceId = generateId('File', filePath);
@@ -856,6 +942,16 @@ export const processImportsFromExtracted = async (
         }
       }
 
+      // PHP: handle namespace-based imports (use statements)
+      if (language === SupportedLanguages.PHP) {
+        const resolved = resolvePhpImport(rawImportPath, composerConfig, allFilePaths, normalizedFileList, allFileList, index);
+        if (resolved) {
+          resolveCache.set(cacheKey, resolved);
+          addImportEdge(filePath, resolved);
+        }
+        continue;
+      }
+
       // Standard resolution (has its own internal cache)
       const resolvedPath = resolveImportPath(
         filePath,