获取错误-致命错误:在 null 上调用成员函数 prepare()

Question

我试图查看相同的问题/答案，但无法弄清楚。

当我访问索引时。它给出错误

"致命错误：在空值上调用成员函数 prepare(( ...">

----------------------------代码是------------------

-------------页1- 索引.php

<?php
include 'inti_test.php';
$user_id =3;
$user = $getFromUserClass->userData($user_id);
?>

-------------------第2页-inti_test.php

<?php
$dsn = 'mysql:host=localhost; dbname=testdb';
$user = 'root';
$pass = 'mypass';
try{
$PDO = new PDO($dsn, $user, $pass);
}catch(PDOException $e){
echo 'Connection error!' .$e->getMessage();
}
//------------------------- 
class User{
protected $pdo;
function __construct($pdo){
$this->pdo =$pdo;
}
public function userData($user_id){
$stmt = $this->pdo->prepare("SELECT * FROM `user_detail_master` WHERE 
`user_id`=:user_id");
$stmt->bindParam(":user_id", $user_id, PDO::PARAM_INT);
$stmt->execute();
return $stmt->fetch(PDO::FETCH_OBJ); 
} 
}
//--------------------- 
global $pdo;
session_start();
$getFromUserClass = new User($pdo);
?>

Answer 1

像那样

<?php
$dsn = 'mysql:host=localhost; dbname=testdb';
$user = 'root';
$pass = 'mypass';
global $pdo;
try{
$pdo = new PDO($dsn, $user, $pass);
}catch(PDOException $e){
echo 'Connection error!' .$e->getMessage();
}
//------------------------- 
class User{
protected $pdo;
function __construct($pdo){
$this->pdo =$pdo;
}
public function userData($user_id){
$stmt = $this->pdo->prepare("SELECT * FROM `user_detail_master` WHERE 
`user_id`=:user_id");
$stmt->bindParam(":user_id", $user_id, PDO::PARAM_INT);
$stmt->execute();
return $stmt->fetch(PDO::FETCH_OBJ); 
} 
}
//--------------------- 
session_start();
$getFromUserClass = new User($pdo);
?>