diff --git a/day_7/part_1.php b/day_7/part_1.php
new file mode 100644
index 0000000..69ca85d
--- /dev/null
+++ b/day_7/part_1.php
@@ -0,0 +1,41 @@
+<?php
+
+// parse tree
+$possible_bags = [];
+
+$rules = explode("\n", file_get_contents('input.txt'));
+
+foreach ($rules as $rule) {
+    [$current_bag, $inside_bags] = explode(' contain ', $rule);
+    $current_bag = substr($current_bag, 0, -5);
+    if ($inside_bags === 'no other bags.') {
+        $possible_bags[$current_bag] = [];
+    } else {
+        $inside_bags = explode(', ', $inside_bags);
+        $parsed_inside_bags = [];
+        foreach ($inside_bags as $inside_bag) {
+            preg_match ('/\d+ (.*) bags?\.?/uU', $inside_bag, $bag);
+            $parsed_inside_bags[] = $bag[1];
+        }
+        $possible_bags[$current_bag] = $parsed_inside_bags;
+    }
+}
+
+function has_shiny_in($total_list, $shiny_list = ['shiny gold'])
+{
+    $at_least_one_add = false;
+    foreach ($total_list as $bag => $item) {
+        if (!in_array($bag, $shiny_list, true) && count(array_intersect($shiny_list, $item)) > 0) {
+            $at_least_one_add = true;
+            $shiny_list[] = $bag;
+        }
+    }
+
+    if ($at_least_one_add) {
+        return has_shiny_in($total_list, $shiny_list);
+    }
+
+    return $shiny_list;
+}
+
+var_dump(has_shiny_in($possible_bags));
\ No newline at end of file