3rd and 2nd day

02/part1.php

@@ -0,0 +1,15 @@
+<?php
+
+$increased   = 0;
+$inputStream = fopen('input', 'r');
+$horizontal  = $depth = 0;
+
+while (($line = fgets($inputStream)) !== false) {
+    [$instruction, $value] = explode(' ', trim($line));
+    match ($instruction) {
+        'down' => $depth += (int)$value,
+        'up' => $depth -= (int)$value,
+        'forward' => $horizontal += (int)$value,
+    };
+}
+echo $depth * $horizontal; // 1635930

02/part2.php

@@ -0,0 +1,23 @@
+<?php
+
+$increased   = 0;
+$inputStream = fopen('input', 'r');
+$horizontal  = $depth = $aim = 0;
+
+while (($line = fgets($inputStream)) !== false) {
+    [$instruction, $value] = explode(' ', trim($line));
+    $value = (int)$value;
+    switch ($instruction) {
+        case 'down':
+            $aim   += $value;
+            break;
+        case 'up':
+            $aim   -= $value;
+            break;
+        case 'forward':
+            $horizontal += $value;
+            $depth      += $value * $aim;
+            break;
+    }
+}
+echo $depth * $horizontal; // 1781819478