How to implement the addition, deletion, check and modification function of the database in php

With the development of the Internet, Web technology is also constantly improving, and PHP, as a mature and powerful Web programming language, has become one of the main choices for Web development. In PHP development, addition, deletion, search, and modification are the most basic operations. This article will describe how to implement these operations.

1. Add data

Adding data is one of the most common operations in web development. In PHP, we usually use MySQL database to store data. Below is a sample code for adding a new user to a MySQL database.

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

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

// 检测连接是否成功
if ($conn->connect_error) {
  die("连接失败: " . $conn->connect_error);
}

// 插入新用户
$sql = "INSERT INTO users (username, password, email)
VALUES ('John', 'Doe', 'john@example.com')";

if ($conn->query($sql) === TRUE) {
  echo "新记录插入成功";
} else {
  echo "Error: " . $sql . "<br>" . $conn->error;
}

// 关闭连接
$conn->close();
?>

In the above example, we use the mysqli_connect() function to connect to the MySQL database and use the INSERT INTO statement to add a new user to the users table. If the insertion operation is successful, the page will output "New record inserted successfully".

2. Deleting data

Deleting data is another common operation in web development. In PHP, we can use the DELETE statement to delete one or more pieces of data from the MySQL database. Below is a sample code to delete a user named "John".

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

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

// 检测连接是否成功
if ($conn->connect_error) {
  die("连接失败: " . $conn->connect_error);
}

// 删除名为“John”的用户
$sql = "DELETE FROM users WHERE username='John'";

if ($conn->query($sql) === TRUE) {
  echo "记录删除成功";
} else {
  echo "Error deleting record: " . $conn->error;
}

// 关闭连接
$conn->close();
?>

In the above example, we use the DELETE FROM statement to delete the user named "John". If the deletion is successful, the page will output "Record Deletion Successful".

3. Querying data

Querying data is one of the most common operations in web development. In PHP, we can use the SELECT statement to query data from the MySQL database. Below is a sample code to query the usernames of all users.

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

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

// 检测连接是否成功
if ($conn->connect_error) {
  die("连接失败: " . $conn->connect_error);
}

// 查询所有用户的用户名
$sql = "SELECT username FROM users";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
  // 输出数据
  while($row = $result->fetch_assoc()) {
    echo "username: " . $row["username"]. "<br>";
  }
} else {
  echo "0 结果";
}

// 关闭连接
$conn->close();
?>

In the above example, we use the SELECT statement to query the usernames of all users. If the query is successful, the page will output the username of each user.

4. Update data

Updating data is another important operation in web development. In PHP, we can update data in the MySQL database using the UPDATE statement. Below is a sample code that updates the email of a user named "John".

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

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

// 检测连接是否成功
if ($conn->connect_error) {
  die("连接失败: " . $conn->connect_error);
}

// 更新名为“John”的用户的电子邮件
$sql = "UPDATE users SET email='john@example.com' WHERE username='John'";

if ($conn->query($sql) === TRUE) {
  echo "记录更新成功";
} else {
  echo "Error updating record: " . $conn->error;
}

// 关闭连接
$conn->close();
?>

In the above example, we use the UPDATE statement to update the email of a user named "John". If the update is successful, the page will output "Record updated successfully".

Summary

Through the introduction of this article, we have learned how to implement basic add, delete, search, and modify operations in PHP. These operations are one of the most common operations in web development, and they are also the basic knowledge that we must master when learning PHP programming.

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