diff --git a/Week_04/id_122/LeetCode_309_122.php b/Week_04/id_122/LeetCode_309_122.php
new file mode 100644
index 00000000..ce390e04
--- /dev/null
+++ b/Week_04/id_122/LeetCode_309_122.php
@@ -0,0 +1,30 @@
+<?php
+/**
+ * Created by PhpStorm.
+ * User: zhangzhengyi
+ * Date: 2019/5/12
+ * Time: 下午4:29
+ */
+class Solution {
+
+    /**
+     * @param Integer[] $prices
+     * @return Integer
+     */
+    function maxProfit($prices) {
+        if (empty($prices)) {
+            return 0;
+        }
+        $n = count($prices);
+        $sell = array(0,);
+        $buy = array(0,);
+        $cool = array(0,);
+        $buy[0] = -$prices[0];
+        for ($i = 1; $i != $n; $i++) {
+            $sell[$i] = max($buy[$i-1] + $prices[$i], $sell[$i-1]);
+            $buy[$i] = max($cool[$i-1] - $prices[$i], $buy[$i-1]);
+            $cool[$i] = max($sell[$i-1], $buy[$i-1], $cool[$i-1]);
+        }
+        return $sell[$n - 1];
+    }
+}
\ No newline at end of file
diff --git a/Week_04/id_122/LeetCode_746_122.php b/Week_04/id_122/LeetCode_746_122.php
new file mode 100644
index 00000000..e1799395
--- /dev/null
+++ b/Week_04/id_122/LeetCode_746_122.php
@@ -0,0 +1,33 @@
+<?php
+/**
+ * Created by PhpStorm.
+ * User: zhangzhengyi
+ * Date: 2019/5/12
+ * Time: 下午4:06
+ */
+class Solution {
+
+    /**
+     * @param Integer[] $cost
+     * @return Integer
+     */
+    function minCostClimbingStairs($cost) {
+        if (empty($cost)) {
+            return 0;
+        }
+        $len = count($cost);
+        if ($len == 1) {
+            return $cost[0];
+        }
+        $tmp1 = $cost[0];
+        $tmp2 = $cost[1];
+        for ($i = 2; $i != $len; $i++) {
+            $tmp = $tmp2;
+            $tmp2 = $cost[$i] + min($tmp1, $tmp2);
+            $tmp1 = $tmp;
+
+        }
+        return min($tmp1, $tmp2);
+
+    }
+}
\ No newline at end of file