


How to solve database connection error in PHP5.6 to PHP7.4 compatibility issue?
How to solve the database connection error in PHP5.6 to PHP7.4 compatibility issue?
As the PHP version is updated, there are compatibility issues from PHP5.6 to PHP7.4. One of the common problems is database connection errors. This article will describe how to solve this problem and give corresponding code examples.
In PHP5.6 and previous versions, we usually use the mysql extension to connect and operate the database. Starting from PHP7.0, the mysql extension has been deprecated and replaced by the mysqli extension and PDO extension. Therefore, when upgrading the code from PHP5.6 to PHP7.4, the database connection code needs to be modified.
First of all, if your code uses the mysql extension, you need to replace it with the mysqli extension. The code to modify the database connection is as follows:
// PHP5.6及之前版本的数据库连接代码 $conn = mysql_connect($servername, $username, $password); mysql_select_db($dbname, $conn); // 修改为PHP7.4的数据库连接代码 $conn = mysqli_connect($servername, $username, $password, $dbname);
In the mysqli extension, the connection function name becomes "mysqli_connect", and the database name needs to be passed in as the fourth parameter.
In addition, it should be noted that starting from PHP7.4, it is no longer supported to use "localhost" as the host name when connecting to the database. If you use "localhost" when connecting to the database, the connection will fail. The solution to this problem is to replace "localhost" with "127.0.0.1" as shown below:
// 使用"127.0.0.1"代替"localhost"连接数据库 $servername = "127.0.0.1";
Next, we need to modify the code that executes the SQL query. In PHP5.6 and previous versions, we usually use the "mysql_query" function to execute SQL queries. In PHP7.4, you need to use the "mysqli_query" function to execute queries. The modified code looks like this:
// PHP5.6及之前版本的SQL查询代码 $result = mysql_query($sql); // 修改为PHP7.4的SQL查询代码 $result = mysqli_query($conn, $sql);
Similarly, the "mysql_query" function needs to be replaced with the "mysqli_query" function and the database connection is passed to the function as the first parameter.
In addition to the mysqli extension, the PDO extension is also a good choice for connecting and operating databases. If you are using PDO extension in your code, you need to modify the database connection code as follows:
// PHP5.6及之前版本的数据库连接代码 $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password); // 修改为PHP7.4的数据库连接代码 $conn = new PDO("mysqli:host=$servername;dbname=$dbname", $username, $password);
In the PDO extension, the database connection method is achieved by instantiating the PDO class, in the parameters "mysql" needs to be replaced with "mysqli".
To summarize, to solve the database connection error in PHP5.6 to PHP7.4 compatibility issues, you first need to replace the mysql extension with the mysqli extension or PDO extension. And note that when connecting to the database, replace "localhost" with "127.0.0.1". Additionally, the code that executes the SQL query needs to be modified accordingly.
Through the above modifications, the code can be successfully upgraded from PHP5.6 to PHP7.4 and compatibility errors caused by database connections can be solved. I hope the content of this article can be helpful to you.
The above is the detailed content of How to solve database connection error in PHP5.6 to PHP7.4 compatibility issue?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

In this chapter, we will understand the Environment Variables, General Configuration, Database Configuration and Email Configuration in CakePHP.

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati

To work with date and time in cakephp4, we are going to make use of the available FrozenTime class.

To work on file upload we are going to use the form helper. Here, is an example for file upload.

In this chapter, we are going to learn the following topics related to routing ?

CakePHP is an open-source framework for PHP. It is intended to make developing, deploying and maintaining applications much easier. CakePHP is based on a MVC-like architecture that is both powerful and easy to grasp. Models, Views, and Controllers gu

Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c

Validator can be created by adding the following two lines in the controller.
