为什么说非对象调用成员函数fetch()

问题描述

<?phpclass Db{ private $dbConfig=['db'=>'mysql','host'=>'localhost','port'=>'3306','user'=>'root','pass'=>'root','charset'=>'utf8','dbname'=>'edu',]; //单例模式 private static $instance = null; public $insertID = null; public $num1 = null; ///数据库的连接 private $conn = null; private function __construct($params) {//初始化参数array_merge($this->dbConfig, $params);//连接数据库$this->connect(); } private function __clone() {// TODO: Implement __clone() method. } public static function getInstance($params=[]) {if(!self::$instance instanceof self){ self::$instance = new self($params);}return self::$instance; } private function connect() {try {$dsn="{$this->dbConfig['db']}:host={$this->dbConfig['host']};port={$this->dbConfig['port']};dbname={$this->dbConfig['dbname']};charset={$this->dbConfig['charset']}";//创建pdo对象$this->conn= new PDO($dsn,$this->dbConfig['user'],$this->dbConfig['pass']); //// $this->conn->query("SET NAMES {$this->dbConfig['charset']}");}catch (PDOException $e){ die('数据库连接失败'.$e->getMessage());} } public function exec($sql) {$num = $this->conn->exec($sql);if($num>0){ if(null !== $this->conn->lastInsertID()) {$this->insertID = $this->conn->lastInsertID(); } $this->num1= $num;}else{ $error = $this->conn->errorInfo(); //0 是错误标识符 1 是错误代码 2 是错误信息 print '操作失败'.$error[0].':'.$error[1].':'.$error[2];} } public function fetch($sql) {return $this->conn->query($sql)->fetch(PDO::FETCH_ASSOC); } public function fetchALl($sql) {return $this->conn->query($sql)->fetch(PDO::FETCH_ASSOC);; }}

问题解答

pdo对象没有获取成功,调用了一个对象成员方法fetch, 检查连接参数