diff --git a/day_10/part_1.php b/day_10/part_1.php
new file mode 100644
index 0000000..d78d377
--- /dev/null
+++ b/day_10/part_1.php
@@ -0,0 +1,29 @@
+<?php
+
+$numbers = array_map('intval', explode("\n", file_get_contents('input.txt')));
+
+sort($numbers);
+
+$difference_of_1 = 0;
+$difference_of_3 = 0;
+
+$current_jolt = 0;
+
+while($current_jolt < max($numbers)) {
+    if (in_array($current_jolt + 1, $numbers, true)) {
+        $current_jolt++;
+        $difference_of_1++;
+        continue;
+    }
+    if (in_array($current_jolt + 3, $numbers, true)) {
+        $current_jolt += 3;
+        $difference_of_3++;
+        continue;
+    }
+}
+
+// your device's built-in adapter is always 3 higher than the highest adapter
+$difference_of_3++;
+$current_jolt += 3;
+
+echo $difference_of_1 * $difference_of_3;
\ No newline at end of file