diff --git a/day_13/part_1.php b/day_13/part_1.php
new file mode 100644
index 0000000..40f1d26
--- /dev/null
+++ b/day_13/part_1.php
@@ -0,0 +1,24 @@
+<?php
+
+$input = file_get_contents('input.txt');
+
+[$earliest_timestamp, $buses] = explode("\n", $input);
+
+$earliest_timestamp = (int) $earliest_timestamp;
+
+$buses = array_filter(
+    array_map(static function ($bus) {
+        return $bus === 'x' ? null : (int) $bus;
+    }, explode(',', $buses))
+);
+
+$timestamp = $earliest_timestamp;
+while (true) {
+    foreach ($buses as $bus) {
+        if ($timestamp % $bus === 0) {
+            echo ($timestamp - $earliest_timestamp) * $bus;
+            exit;
+        }
+    }
+    $timestamp++;
+}
\ No newline at end of file