How to make database connection in PHP?

PHP is a server-side scripting language widely used in website development, and database connection is an indispensable part of PHP development, and its importance is self-evident. In this article, we will discuss how to make database connections in PHP for better website and application development.

1. Basic concepts of database connections

In PHP, we need to use database connections to interact with the database. Database connection refers to connecting to the database through a program and performing corresponding operations to achieve functions such as adding, modifying, deleting, and querying data.

Database connection is achieved through a specialized database extension program. The most commonly used database extensions in PHP include MySQL, PostgreSQL and SQLite. Before using these extensions, we need to install the corresponding database software on the server.

2. MySQL database connection

MySQL is a well-known relational database management system that provides efficient, stable and secure data storage and access services. In PHP, we can implement MySQL database connection through MySQLi and PDO.

2.1 MySQLi extension

MySQLi is the abbreviation of MySQL Improved. It is an extension recommended for PHP to interact with MySQL. It provides more functions and better performance. The following is the basic code for MySQLi to implement database connection:

<?php
  $servername = "localhost";
  $username = "root";
  $password = "123456";
  $dbname = "mydb";

  // 创建连接
  $conn = new mysqli($servername, $username, $password, $dbname);

  // 检测连接
  if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
  }
  echo "连接成功";
?>

In the above code, we first define the database-related information, including host name, user name, password and database name. Then, we create a MySQLi connection object using the mysqli() function and store it in the variable $conn. Finally, we use the connect_error attribute to detect whether the connection is successful. If the connection fails, an error message is output.

2.2 PDO extension

PDO is the abbreviation of PHP Data Objects, which is a flexible and object-oriented database operation method. Compared to the MySQLi extension, PDO can connect to many different types of databases. The following is the basic code for PDO to implement MySQL database connection:

<?php
  $servername = "localhost";
  $username = "root";
  $password = "123456";
  $dbname = "mydb";

  try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    // 设置 PDO 错误模式为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "连接成功";
  } catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
  }
?>

In the above code, we first define the database-related information, including host name, user name, password and database name. Then, we create a PDO connection object using the PDO() function and store it in the variable $conn. Finally, we use the setAttribute() function to set the error mode of PDO and handle connection failure in the try-catch statement.

3. PostgreSQL database connection

PostgreSQL is another commonly used relational database management system, which provides reliable and efficient data management functions. In PHP, we can implement PostgreSQL database connection through PDO extension. The following is the basic code to implement a PostgreSQL database connection:

<?php
  $servername = "localhost";
  $port = "5432";
  $dbname = "mydb";
  $username = "root";
  $password = "123456";

  try {
    $conn = new PDO("pgsql:host=$servername;port=$port;dbname=$dbname;user=$username;password=$password");
    // 设置 PDO 错误模式为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "连接成功";
  } catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
  }
?>

In the above code, we use the PDO() function to create a PDO connection object and store it in the variable $conn. We specify connection information such as host name, port number, database name, user name and password by specifying different parameters.

4. SQLite database connection

SQLite is a small relational database management system that is often used to develop lightweight applications in PHP. In PHP, we can implement SQLite database connection through PDO extension. The following is the basic code to implement a SQLite database connection:

<?php
  $dbname = "mydb.sqlite";

  try {
    $conn = new PDO("sqlite:$dbname");
    // 设置 PDO 错误模式为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "连接成功";
  } catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
  }
?>

In the above code, we use the PDO() function to create a PDO connection object and store it in the variable $conn. We specify the connection information of the SQLite database by specifying sqlite: followed by the database file name.

5. Summary

In this article, we discussed ways to implement MySQL, PostgreSQL and SQLite database connections in PHP. We can see that by using different extensions and specifying different connection information, we can easily connect to different databases and achieve the required data management and operation functions. In practice, we need to choose a suitable database connection method according to specific needs and scenarios to obtain the best performance and security.

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