Execute sort less times

By sorting every call, we are just pumping up the system.
There is no need to do this, only when we need the files.

Author: jaapio

packages/guides/src/Files.php

@@ -33,17 +33,18 @@ final class Files implements IteratorAggregate, Countable
 
     public function add(string $filename): void
     {
-        if (in_array($filename, $this->files, true)) {
+        if (array_key_exists($filename, $this->files)) {
             return;
         }
 
-        $this->files[] = $filename;
-        sort($this->files, SORT_NATURAL | SORT_FLAG_CASE);
+        $this->files[$filename] = $filename;
     }
 
     /** @return Iterator<string> */
     public function getIterator(): Iterator
     {
+        sort($this->files, SORT_NATURAL | SORT_FLAG_CASE);
+
         return new ArrayIterator($this->files);
     }