[2017-12-01] Solution for both puzzles

Makefile

@@ -1,6 +1,8 @@
 .PHONY: day1 day2 day3 day4 day5 day6 day7 day8 day9 day10 day11 day12 day13 day14 day15 day16 day17 day18 day19 day20 day21 day22 day23 day24 day25
 
 day1:
+	php day1/main.php
+
 day2:
 day3:
 day4:

day1/main.php

@@ -0,0 +1,24 @@
+<?php
+// http://adventofcode.com/2017/day/1
+
+function puzzle(string $input, bool $dynamicOffset) : int
+{
+    $len = strlen($input);
+    $offset = $dynamicOffset ? $len / 2 : 1;
+    $output = 0;
+
+    // Duplicate input so we don't have to handle the circular event
+    $input = $input.$input;
+
+    for ($x = 0; $x <= ($len - 1); $x++) {
+        $currentNumber = (int) $input[$x];
+        $nextNumber = (int) $input[$x + $offset];
+
+        // If we got the right number, add it to result
+        if ($currentNumber === $nextNumber) {
+            $output += $currentNumber;
+        }
+    }
+
+    return $output;
+}