初始化

core/db/Db.php

@@ -0,0 +1,40 @@
+<?php
+namespace core\db;
+
+use PDO;
+use PDOException;
+
+/**
+ * 数据库操作类
+ */
+class Db
+{
+    private static $pdo = null;
+
+    public static function pdo()
+    {
+        if (self::$pdo !== null) {
+            return self::$pdo;
+        }
+
+        try {
+            $dsn    = sprintf('mysql:host=%s;dbname=%s;charset=utf8mb4', DB_HOST, DB_NAME);
+            $option = array(
+                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
+                // 强制开启查询缓冲：避免「2014 Cannot execute queries while other
+                // unbuffered queries are active」。该连接在多处被复用（单例），
+                // 若不缓冲，前一条语句的结果集未取完就会阻塞后续查询。
+                PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true,
+            );
+
+            $pdo = new PDO($dsn, DB_USER, DB_PASS, $option);
+            // 部分环境在构造选项里设置不生效，再显式 setAttribute 兜底
+            $pdo->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
+            return self::$pdo = $pdo;
+        } catch (PDOException $e) {
+            error_log('DB connection error: ' . $e->getMessage());
+            exit('数据库连接失败，请联系管理员');
+        }
+    }
+}