diff --git a/Makefile b/Makefile
index a8c5e17..8703c1e 100644
--- a/Makefile
+++ b/Makefile
@@ -10,6 +10,8 @@ day3:
 	php day3/main.php
 
 day4:
+	php day4/main.php
+
 day5:
 day6:
 day7:
diff --git a/day4/main.php b/day4/main.php
new file mode 100644
index 0000000..0edce70
--- /dev/null
+++ b/day4/main.php
@@ -0,0 +1,39 @@
+<?php
+// https://adventofcode.com/2018/day/4
+
+function puzzle1(array $logEntries)
+{
+    $sleepMatrix = [];
+    $guardOnDuty = -1;
+
+    foreach ($logEntries as $entry) {
+        preg_match(
+            '/\[(\d{4})-(\d\d)-(\d\d)\s(\d\d):(\d\d)\]\s(.+)/',
+            $entry,
+            $matches
+        );
+
+        print_r($matches);
+    }
+}
+
+echo 'First challange sample:'.PHP_EOL;
+echo puzzle1([
+    '[1518-11-01 00:00] Guard #10 begins shift',
+    '[1518-11-01 00:05] falls asleep',
+    '[1518-11-01 00:25] wakes up',
+    '[1518-11-01 00:30] falls asleep',
+    '[1518-11-01 00:55] wakes up',
+    '[1518-11-01 23:58] Guard #99 begins shift',
+    '[1518-11-02 00:40] falls asleep',
+    '[1518-11-02 00:50] wakes up',
+    '[1518-11-03 00:05] Guard #10 begins shift',
+    '[1518-11-03 00:24] falls asleep',
+    '[1518-11-03 00:29] wakes up',
+    '[1518-11-04 00:02] Guard #99 begins shift',
+    '[1518-11-04 00:36] falls asleep',
+    '[1518-11-04 00:46] wakes up',
+    '[1518-11-05 00:03] Guard #99 begins shift',
+    '[1518-11-05 00:45] falls asleep',
+    '[1518-11-05 00:55] wakes up',
+]).PHP_EOL; // 240