Fatal error: Call to a member function prepare()?

Question

我正在尝试使用 PDO 查询数据库，但我遇到了一个致命错误任何人帮助实际发生的事情...

Config.php

<?php


class Config{
    public static function get($path = null){
        if($path){
             $config = $GLOBALS['config'];
             $path = explode('/',$path);


             foreach ($path as $bit) {
                 if (isset($config[$bit])) {
                        $config = $config[$bit];
                     }
                 }
                 return $config;
        }
        return false;
    }
 }

init.php

<?php
    session_start();

    $GLOBALS['config'] = array(
        'mysql' => array(
            'host' => '127.0.0.1',
            'username' => 'root',
            'password' => 'rajaraman',
            'db' => 'sms'
        ),
    'remember' => array(
        'cookie_name' => 'hash' ,
        'cookie_expiry' => 604800
        ),
        'session' =>  array(
            'session_name' => 'user' 
        )
     );
    spl_autoload_register(function($class){
        require_once 'classes/' .$class. '.php';
    }); 
    require_once 'functions/sanitize.php';
?>

index.php

<?php
  require_once 'core/init.php';

  $user =  Db::getInstance()->query("SELECT username FROM users WHERE username = ?",array('raja')); 
  if ($user->error) 
  {
      echo "No user";
  }
  else{
    echo "OK!";
  }
  ?>

?>

Db.php

<?php
    class Db
    {
        private static $_instance = null;
        private $_pdo,
                $_query,
                $_error=false,
                $_results,
                $_count=0;
        private function __constructs()
        {
            try
            {
                $this->_pdo =new PDO("mysql:host=" .Config::get('mysql/host') . ";dbname=" .Config::get('mysql/db'),Config::get('mysql/username'),Config::get('mysql/password'));
            }
            catch(PDOException $e)
            {
                    die($e->getMessage());
            }

        }

        public static function getInstance()
        {
            if (!isset(self::$_instance)) 
            {
                self::$_instance = new Db();
                # code...
            }
            return self::$_instance;
        }
        public function query($sql,$params=array())
        {
            $this->_error = false;
            if($this->_query = $this->_pdo->prepare($sql))
            {   
                $x=1;
                if (count($params)) 
                {
                    foreach ($params as $param ) 
                    {
                        $this->_query->bindvalue($x,$param);
                        $x++;
                    }
                }
                if ($this->_query->execute())
                 {
                        $this->_results = $this->fetchAll(PDO::FETCH_OBJ);
                        $this->_count = $this->_query->rowCount();
                 }  
                 else 
                 {
                    $this->error=true;
                 }
            }
            return $this;               
        }
        public function error(){
            return $this->error;
        }
    }
?>

当我运行使用 xampp 服务器时它显示错误，这是非对象上的致命错误...它在 prepare 方法中的实际错误。

致命错误：在 C:\xampp\htdocs\Student Management system\classes\Db.php 中的非对象上调用成员函数 prepare() 第 35 行

Answer 1

"Call to a member function prepare() on a non-object..."表示$this->_pdo->prepare($sql))中的对象“_pdo”不存在。

反过来，这意味着构造函数（应该初始化 _pdo）从未被调用。

因为它应该被命名为 __construct()（而不是“__constructs”）。

此外，正如 Fred -ii- 已经指出的那样，bindValue() 拼写错误。

并且，为了完整起见：

$this->_results = $this->_query->fetchAll(PDO::FETCH_OBJ);

Fatal error: Call to a member function prepare()?

Fatal error: Call to a member function prepare()?

php

mysql

pdo

phpmyadmin