[2017-12-04] Solutions for both puzzles

Makefile

@@ -10,6 +10,8 @@ day3:
 	php day3/main.php
 
 day4:
+	php day4/main.php
+
 day5:
 day6:
 day7:

day4/main.php

@@ -0,0 +1,44 @@
+<?php
+// https://adventofcode.com/2017/day/4
+
+function puzzle1(string $input) : int
+{
+    $rows = explode(PHP_EOL, $input);
+    $sum = 0;
+
+    foreach ($rows as $row) {
+        $words = explode(' ', $row);
+
+        if (count($words) === count(array_unique($words))) {
+            $sum++;
+        }
+    }
+
+    return $sum;
+}
+
+function puzzle2(string $input) : int
+{
+    $rows = explode(PHP_EOL, $input);
+    $sum = 0;
+
+    foreach ($rows as $row) {
+        $words = explode(' ', $row);
+
+        // Sort letters in alphabetical order in words
+        $words = array_map(function($value) {
+            $letters = str_split($value, 1);
+
+            sort($letters);
+
+            return implode('', $letters);
+        }, $words);
+
+        // Count unique words
+        if (count($words) === count(array_unique($words))) {
+            $sum++;
+        }
+    }
+
+    return $sum;
+}