Refactor method; return early when match is found

Author: tvdijen

src/XML/DOMDocumentFactory.php

@@ -153,20 +153,18 @@ public static function normalizeDocument(Dom\XMLDocument $doc): Dom\XMLDocument
 
     /**
      * @param \Dom\Element $elt
-     * @param string $prefix
+     * @param string|null $prefix
      */
-    public static function lookupNamespaceURI(Dom\Element $elt, string $prefix): ?string
+    public static function lookupNamespaceURI(Dom\Element $elt, ?string $prefix): ?string
     {
         /** @var \Dom\NamespaceInfo[] $namespaces */
         $namespaces = $elt->ownerDocument->documentElement->getInScopeNamespaces();
 
         $xmlnsAttributes = [];
         foreach ($namespaces as $ns) {
-            $xmlnsAttributes[$ns->prefix] = $ns->namespaceURI;
-        }
-
-        if (array_key_exists($prefix, $xmlnsAttributes)) {
-            return $xmlnsAttributes[$prefix];
+            if ($ns->prefix === $prefix) {
+                return $ns->namespaceURI;
+            }
         }
 
         return null;