diff --git a/day_18/part_1.php b/day_18/part_1.php
new file mode 100644
index 0000000..af48451
--- /dev/null
+++ b/day_18/part_1.php
@@ -0,0 +1,53 @@
+<?php
+
+$operations = explode("\n", file_get_contents('input.txt'));
+
+$results = [];
+foreach ($operations as $i => $operation) {
+    $operation = evaluateParentheses($operation);
+    $operation = evaluateOperation($operation);
+    $results[] = (int) $operation;
+    echo sprintf('Line %u : %u%s', $i+1, $operation, "\n");
+}
+
+echo array_sum($results);
+/**
+ * @param string $operation
+ *
+ * @return false|float|int
+ * @throws \Exception
+ */
+function evaluateOperation(string $operation)
+{
+    while (!is_numeric($operation)) {
+        $operation = preg_replace_callback(
+            '/^(\d+) (\+|\*) (\d+)/',
+            static function ($matches) {
+                switch ($matches[2]) {
+                    case '+':
+                        return (int)$matches[1] + (int)$matches[3];
+                    case '*':
+                        return (int)$matches[1] * (int)$matches[3];
+                    default:
+                        throw new \Exception('Unknown Operation ' . var_export($matches, true));
+                }
+            },
+            $operation
+        );
+    }
+
+    return $operation;
+}
+
+function evaluateParentheses($operation)
+{
+    $result = preg_replace_callback('/\(([^\)\(]+)\)/', static function ($matches) {
+        return evaluateOperation($matches[1]);
+    }, $operation);
+
+    if ($result === $operation || $result === null) {
+        return $operation;
+    }
+
+    return evaluateParentheses($result);
+}
diff --git a/day_18/part_2.php b/day_18/part_2.php
new file mode 100644
index 0000000..fa029ad
--- /dev/null
+++ b/day_18/part_2.php
@@ -0,0 +1,57 @@
+<?php
+
+$operations = explode("\n", file_get_contents('input.txt'));
+
+$results = [];
+foreach ($operations as $i => $operation) {
+    $operation = evaluateParentheses($operation);
+    $operation = evaluateOperation($operation);
+    $results[] = (int) $operation;
+    echo sprintf('Line %u : %u%s', $i+1, $operation, "\n");
+}
+
+echo array_sum($results);
+/**
+ * @param string $operation
+ *
+ * @return false|float|int
+ * @throws \Exception
+ */
+function evaluateOperation(string $operation)
+{
+    while (!is_numeric($operation)) {
+        $original_operation = $operation;
+        $operation = preg_replace_callback(
+            '/(\d+) \+ (\d+)/',
+            static function ($matches) {
+                return (int)$matches[1] + (int)$matches[2];
+            },
+            $operation
+        );
+
+        if ($original_operation === $operation) {
+            $operation = preg_replace_callback(
+                '/(\d+) \* (\d+)/',
+                static function ($matches) {
+                    return (int)$matches[1] * (int)$matches[2];
+                },
+                $operation
+            );
+        }
+    }
+
+    return $operation;
+}
+
+function evaluateParentheses($operation)
+{
+    $result = preg_replace_callback('/\(([^\)\(]+)\)/', static function ($matches) {
+        return evaluateOperation($matches[1]);
+    }, $operation);
+
+    if ($result === $operation || $result === null) {
+        return $operation;
+    }
+
+    return evaluateParentheses($result);
+}