How to modify the contents of a database table using PHP

PHP is a widely used server-side scripting language, which is mainly used for web development. Compared with the front-end, back-end development needs to be applied to database operations to enhance the data storage of web applications. In PHP, we can use the MySQL database, which provides PHP with powerful data storage and query capabilities. In actual web development, we usually need to create, delete, and update data in database tables. This article will introduce how to use PHP to modify the contents of database tables.

1. Connect to the database

In PHP, we can use mysqli or PDO to connect to the MySQL database. The code to connect to the database is as follows:

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

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

// 检查连接是否成功
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
} 
echo "Connected successfully";
?>

The above code creates a connection named $conn, which is used to access the database. If the connection is successful, "Connected successfully" will be output.

2. Obtain data

In PHP, we use SQL statements to query the contents of the database table. Here is a simple SQL statement example to query all records in the table named "users":

SELECT * FROM users;

In the actual PHP script, we can use the mysqli_query function to execute the SQL statement and get the results. The following is a sample code:

$sql = "SELECT * FROM users";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出每一行的数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
    }
} else {
    echo "0 results";
}

The above code stores the query results in $result and uses the mysqli_fetch_assoc function to output the data for each row.

3. Update data

In PHP, we can use SQL statements to update the contents of the database table. Below is a simple SQL statement example to update the record with id 1 in the table named "users":

UPDATE users SET firstname='John', lastname='Doe' WHERE id=1;

In the actual PHP script, we can use the mysqli_query function to execute the SQL statement and update data. The following is a sample code:

$sql = "UPDATE users SET firstname='John', lastname='Doe' WHERE id=1";

if (mysqli_query($conn, $sql)) {
    echo "Record updated successfully";
} else {
    echo "Error updating record: " . mysqli_error($conn);
}

The above code will update the record with id 1 in the table named "users" and output the update results.

Summary

In this article, we introduced the use of PHP to modify database tables. First we need to connect to the database, secondly we can use SQL statements to query the contents of the database table, and finally we can use SQL statements to update the contents of the database table. Learning PHP database operations well will help you better create web applications and strengthen your ability to control data.

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