mysqli_insert_id 不适用于 php OOP 方法 [英] mysqli_insert_id is not working on php OOP method

问题描述

我正在测试使用 mysqli_insert_id 获取最后一个 auto_increment_ID 的功能.当我发现如果我使用两种不同的方法，结果是不同的时，我感到很困惑.

I am testing the function of getting last auto_increment_ID by using mysqli_insert_id . I feel quite confuse when I find out the if i use 2 different methods, the results are different.

方法一

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}

$sql = "INSERT into item(uid,item_id,item_name,item_price,item_quantity) 
                    VALUES('1','0','hhh','23','23');";

if (mysqli_query($conn, $sql)) {
$last_id = mysqli_insert_id($conn);
echo "New record created successfully. Last inserted ID is: " . $last_id;
} else {
echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

mysqli_close($conn);
?>

这种程序方式有效，因为我可以获得最后一个 ID.

This Procedural way is working as i can get the last ID.

方法二

db.php

class db{

protected $db_host;
protected $db_name;
protected $db_user_name;
protected $db_pass;

public function __construct($host,$db_n,$user_n,$pass) {
    $this->db_host=$host;
    $this->db_name=$db_n;
    $this->db_user_name=$user_n;
    $this->db_pass=$pass;
}

public function conn(){
    return mysqli_connect($this->db_host, $this->db_user_name, $this->db_pass, $this->db_name);
}
}

test.php

require "db.php";

$db=new db('localhost','bs','root','');

$sql = "INSERT into item(uid,item_id,item_name,item_price,item_quantity) 
                    VALUES('1','0','hhh','23','23');";

if (mysqli_query($db->conn(), $sql)) {
$last_id = mysqli_insert_id($db->conn());
echo "New record created successfully. Last inserted ID is: " . $last_id;
} else {
echo "Error: " . $sql . "<br>" . mysqli_error($db->conn());
}

mysqli_close($db->conn());

这个方法根本行不通……它会得到结果 0 .有谁知道我哪里出错了?

this method simply doesn't work... It will get the result 0 . Anyone know where did i go wrong?

推荐答案

只初始化一次 ->conn() 方法，然后重复使用它.每次调用都会创建一个新调用:

Only initialize ->conn() method once, then just reuse it. Every invocation creates a new one:

$db = new db('localhost','bs','root','');
$connection = $db->conn(); // initialize once
$sql = "INSERT into item(uid,item_id,item_name,item_price,item_quantity) 
                    VALUES('1','0','hhh','23','23');";

if (mysqli_query($connection, $sql)) {
    $last_id = mysqli_insert_id($connection);
    echo "New record created successfully. Last inserted ID is: " . $last_id;
} else {
    echo "Error: " . $sql . "<br>" . $connection->error;
}

$connection->close();

或者使用面向对象的接口(->insert_id 属性):

Or using object oriented interface (->insert_id property):

$db = new db('localhost','bs','root','');
$connection = $db->conn(); // initialize once
$sql = "INSERT into item(uid,item_id,item_name,item_price,item_quantity) 
                    VALUES('1','0','hhh','23','23');";

if($connection->query($sql)) {
    $last_id = $connection->insert_id;
    echo "New record created successfully. Last inserted ID is: " . $last_id;
} else {    
    echo "Error: " . $sql . "<br>" . $connection->error;
}

$connection->close();

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