Examples to explain how PHP operates mysql to add, delete, modify and query

PHP and MySQL are one of the most commonly used technologies in WEB application development, especially in data management. This article will introduce how PHP implements add, delete, modify and query operations through MySQL. Solid basic knowledge and practical experience will better help you master these skills.

1. Connect to MySQL database

First you need to connect to a MySQL database. We can connect to the MySQL database through the following PHP code:

<?php
$servername = "localhost"; // 数据库主机名
$username = "root"; // 登录数据库的用户名
$password = ""; // 登录数据库的密码

// 创建连接
$conn = mysqli_connect($servername, $username, $password);

// 检查连接是否成功
if (!$conn) {
   die("连接失败: " . mysqli_connect_error());
}
echo "连接成功";
?>

This code will return "Connect Success" line indicates that PHP has successfully connected to the MySQL database.

2. Query the MySQL database

To query data from the MySQL database, you need to use the SELECT statement. The following PHP code will query the "posts" table in the "blog" database:

<?php
// 查询语句
$sql = "SELECT * FROM posts";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
   // 输出每一行数据
   while($row = mysqli_fetch_assoc($result)) {
      echo "id: " . $row["id"]. " - 标题: " . $row["title"]. " - 作者: " . $row["author"]. "<br>";
   }
} else {
   echo "0 结果";
}

// 关闭连接
mysqli_close($conn);
?>

This code will output all article IDs, titles, and authors. You can change the output information to meet your needs.

3. Insert MySQL data

To insert data into the MySQL database, you need to use the INSERT statement. The following is an example of inserting data into the "posts" table:

<?php
$title = "新文章标题";
$content = "新文章内容";
$author = "张三";

// Insert into query
$sql = "INSERT INTO posts (title, content, author)
VALUES ('$title', '$content', '$author')";

if (mysqli_query($conn, $sql)) {
   echo "成功插入数据";
} else {
   echo "错误: " . $sql . "<br>" . mysqli_error($conn);
}

// 关闭连接
mysqli_close($conn);
?>

4. Update MySQL data

To update data in the MySQL database, you need to use the UPDATE statement. The following is an example of updating a specific post in the "posts" table:

<?php
$id = "1";
$new_title = "新文章标题";
$new_content = "新文章内容";

// 更新语句
$sql = "UPDATE posts SET title='$new_title', content='$new_content' WHERE id=$id";

if (mysqli_query($conn, $sql)) {
   echo "数据更新成功";
} else {
   echo "错误: " . $sql . "<br>" . mysqli_error($conn);
}

// 关闭连接
mysqli_close($conn);
?>

This code will update the title and content of the post with ID 1 in the database to the new one.

5. Delete MySQL data

To delete data from the MySQL database, use the DELETE statement. Here is an example of deleting a specific post from the "posts" table:

<?php
$id = "1";

// 删除语句
$sql = "DELETE FROM posts WHERE id=$id";

if (mysqli_query($conn, $sql)) {
   echo "数据删除成功";
} else {
   echo "错误: " . $sql . "<br>" . mysqli_error($conn);
}

// 关闭连接
mysqli_close($conn);
?>

This method will delete the post with ID 1.

Finally, good practices and sufficient knowledge reserves can help in data management. The more often you practice, the more proficient you will be in data management skills. Everyone is encouraged to practice more and become proficient in data management techniques.

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