fix bug on merge node logic in delete key function

Author: sandersyao

B-Tree/BTree/Delete.class.php

@@ -265,11 +265,27 @@ private function _canMergeImmediately (BTree_Node $parent, BTree_Node $nextParen
      * @param   bool        $isSaveParent   上级节点是否已保存
      * @return  BTree_Node                  左侧节点
      */
-    private function _mergeStore (BTree_Node $left, BTree_Node $right, BTree_Node $parent, BTree_Node $nextParent, $midKey, $midValue, $key, $isSaveParent = false) {
+    private function _mergeStore (
+        BTree_Node $left,
+        BTree_Node $right,
+        BTree_Node $parent,
+        BTree_Node $nextParent,
+        $midKey,
+        $midValue,
+        $key,
+        $isSaveParent = false
+    ) {
+
+        if (BTree_Validate::value($left->match($key))) {
+
+            $left->delete($key, BTree_Node::DELETE_FLAG_RIGHT);
+        } else {
+
+            $right->delete($key, BTree_Node::DELETE_FLAG_RIGHT);
+        }
 
         $left->insert($midKey, $midValue, $left->rightBorderChild(), $right->leftBorderChild());
         $left->merge($right);
-        $left->delete($key, BTree_Node::DELETE_FLAG_RIGHT);
         $parent->delete($midKey, BTree_Node::DELETE_FLAG_RIGHT);
 
         if (!$isSaveParent) {

B-Tree/BTree/Node.class.php

@@ -143,12 +143,14 @@ public  function delete ($key, $deleteFlag = self::DELETE_FLAG_LEFT) {
 
     public  function leftBorderChild () {
 
-        return  $this->_children[0];
+        reset($this->_children);
+
+        return  count($this->_children) > 0 ? current($this->_children) : 0;
     }
 
     public  function rightBorderChild () {
 
-        return  end($this->_children);
+        return  count($this->_children) > 0 ? end($this->_children) : 0;
     }
 
     public  function pointerLeftChild ($pointer) {
@@ -233,7 +235,9 @@ public  function replaceKey ($keyOld, $keyNew, $valueNew) {
 
     public  function isLeaf () {
 
-        return  0 == count($this->_children) || $this->_children[0] <= 0;
+        reset($this->_children);
+
+        return  0 == count($this->_children) || current($this->_children) <= 0;
     }
 
     /**
@@ -250,7 +254,9 @@ private function _dichotomySearch ($key, $list, $offset = 0) {
 
         if (1 == $count) {
 
-            return  strval($key) > strval($list[0]) ? $offset + 1   : $offset;
+            reset($list);
+
+            return  strval($key) > strval(current($list)) ? $offset + 1   : $offset;
         }
 
         $offsetMiddle   = floor($count / 2);
@@ -266,7 +272,7 @@ public  function getLeftBorderKey () {
 
         $keyList    = array_keys($this->_data);
 
-        return  $keyList[0];
+        return  current($keyList);
     }
 
     public  function getRightBorderKey () {