How to use php to operate the database (add, delete, modify, check)

PHP is a very popular web programming language. It is easy to learn and can be used to create dynamic websites and web applications. The most common operation is CRUD. This article will introduce these operations in PHP in detail.

Add data

In PHP, adding data is usually done by inserting a row of new data into the database. First we need to connect to the database, then build the SQL statement and send it to the server. Here is a sample code:

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);
// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 构建 SQL 语句
$sql = "INSERT INTO MyGuests (firstname, lastname, email)
VALUES ('John', 'Doe', 'john@example.com')";

// 发送 SQL 语句到服务器
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 this example, we first establish a connection to the database and check whether the connection is successful. Then, we use SQL statements to insert new data into the MyGuests table, and finally output the insertion results and close the connection.

Deleting data

Deleting data is usually done by sending a DELETE statement to the database. Here is a sample code:

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);
// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 构建 SQL 语句
$sql = "DELETE FROM MyGuests WHERE id=3";

// 发送 SQL 语句到服务器
if ($conn->query($sql) === TRUE) {
    echo "记录删除成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

// 关闭连接
$conn->close();

In this example, we first create a connection to the database and check whether the connection is successful. Then we use the DELETE statement to delete the data with id 3 from the MyGuests table and output the deletion result. Finally close the connection.

Update data

Updating data is usually done by sending an UPDATE statement to the database. Here is a sample code:

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);
// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 构建 SQL 语句
$sql = "UPDATE MyGuests SET firstname='Peter' WHERE id=1";

// 发送 SQL 语句到服务器
if ($conn->query($sql) === TRUE) {
    echo "记录更新成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

// 关闭连接
$conn->close();

In this example, we first create a connection to the database and check whether the connection is successful. Then we use the UPDATE statement to change the firstname of the data with id 1 to Peter. Finally, the update results are output and the connection is closed.

Querying data

Querying data is usually done by sending a SELECT statement to the database. Here is a sample code:

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);
// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 构建 SQL 语句
$sql = "SELECT * FROM MyGuests";
$result = $conn->query($sql);

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

// 关闭连接
$conn->close();

In this example, we first create a connection to the database and check whether the connection is successful. We then use a SELECT statement to get all the data from the MyGuests table and use PHP's while loop to output all the data. Finally we close the connection.

Summary

In PHP, only adding, deleting, modifying and checking may be the most common operation. In this article, we detail how to add, delete, update, and query data to a database via PHP. If you are a developer, I believe this article is very useful to you.

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