How to perform database queries using PHP built-in functions?

PHP built-in functions can be used to execute database queries, including: mysqli_query(): executes queries and returns results. PDOStatement: Prepare queries and bind parameters to prevent SQL injection. mysqli_affected_rows(): Get the number of rows affected by the query (using mysqli). PDOStatement::rowCount(): Gets the number of rows affected by the query (using PDO). mysqli_close(): Close the mysqli database connection. PDO: Automatically close the PDO connection after the script is executed.

Use PHP built-in functions to perform database queries

PHP provides a large number of built-in functions that can be used to perform database queries. This article explains how to use some commonly used PHP database built-in functions and provides practical examples.

Required tools:

• PHP 7 or higher
• MySQL or other database that supports PDO
• Database connection information

Connect to the database:

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

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e) {
    die("连接失败：" . $e->getMessage());
}

Use mysqli_query() function query:

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

Get query results:

if ($result) {
    while($row = $result->fetch(PDO::FETCH_ASSOC)) {
        echo "ID: " . $row["id"]. "  姓名: " . $row["name"]. "<br>";
    }
}

Use pdo to query data:

How to use this function Similar to the mysqli_query() function, but a PDOStatement object needs to be prepared in advance.

$stmt = $conn->prepare($sql);
$stmt->execute();

while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
    echo "ID: " . $row["id"]. "  姓名: " . $row["name"]. "<br>";
}

Use pdo for prepared queries:

Prepared queries allow you to bind parameters to prevent SQL injection.

$sql = "INSERT INTO users (name, email) VALUES (?, ?)";
$stmt = $conn->prepare($sql);
$stmt->execute([$name, $email]);

Use mysqli_affected_rows() Get the number of affected rows:

$num_rows = mysqli_affected_rows($conn);
echo "受影响的行数：" . $num_rows;

Use PDO Get the number of affected rows Number of rows affected:

$num_rows = $stmt->rowCount();
echo "受影响的行数：" . $num_rows;

Use mysqli_close() Close the database connection:

mysqli_close($conn);

Use PDO Close the database connection:

There is no need to manually close the PDO connection. When the script is finished executing, it will automatically close.

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