PHP performs add, delete, modify and query operations on MySQL database

With the rapid development of the Internet, website functions are becoming more and more complex, and data interactions are becoming more and more frequent. As the most popular back-end language, PHP is increasingly used. In web development, interaction with databases is an important link. Commonly used databases include MySQL, Oracle, SQL Server, etc. Based on examples, this article introduces how to implement addition, deletion, modification and query operations on MySQL database through PHP language.

First, we need to connect to the MySQL database using PHP. In PHP, you can use the mysqli function library to operate the MySQL database. The mysqli function library is an extension library of PHP that provides many functions for operating MySQL database.

Connect to the database:
You need to use the mysqli_connect() function to connect to the MySQL database. This function has 4 parameters: server address, user name, password, and database name. Among them, the server address and user name are required, and the password and database name are optional. The code is as follows:

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "testDB";

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

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

If the connection is successful, the "Connection Successful" message will be output. If the connection fails, a "Connection failed" message and detailed error information will be output.

Add data:
Next, we will demonstrate how to add data to the MySQL database through PHP. In MySQL, use the INSERT statement to insert one or more rows of data into a table. The code is as follows:

$name = 'Tom';
$age = 18;
$sql = "INSERT INTO user (name, age) VALUES ('$name', '$age')";

if (mysqli_query($conn, $sql)) {
    echo "数据插入成功";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

This code is used to insert a row of data into the table named "user", which contains two fields: "name" and "age". If the insertion operation is successful, the "data insertion successful" message will be output, otherwise an error message will be output.

Modify data:
Next, we will demonstrate how to modify the data in the MySQL database through PHP. In MySQL, use the UPDATE statement to modify data in a table. The code is as follows:

$age = 20;
$sql = "UPDATE user SET age='$age' WHERE name='Tom'";

if (mysqli_query($conn, $sql)) {
    echo "数据修改成功";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

This code is used to modify the "age" field of the record named "Tom" to 20. If the modification operation is successful, the "data modification successful" message will be output, otherwise an error message will be output.

Querying data:
Next, we will demonstrate how to query data in the MySQL database through PHP. In MySQL, use the SELECT statement to query data from a table. The code is as follows:

$sql = "SELECT * FROM user";

$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出每行数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "name: " . $row["name"]. " - age: " . $row["age"]. "<br>";
    }
} else {
    echo "0 结果";
}

This code is used to query all rows from the table named "user" and output the "name" and "age" fields of each row. If there is data in the table, the query results will be output; otherwise, "0 results" will be output.

Deleting data:
Finally, we will demonstrate how to delete data in the MySQL database through PHP. In MySQL, use the DELETE statement to delete data from a table. The code is as follows:

$sql = "DELETE FROM user WHERE name='Tom'";

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

This code is used to delete the record named "Tom". If the deletion operation is successful, the "data deletion successful" message will be output, otherwise an error message will be output.

To sum up, this example demonstrates how to use PHP to add, delete, modify and query the MySQL database. Of course, in actual development, we need to choose an appropriate database operation method according to our needs, and pay attention to preventing security issues such as SQL injection.

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