Application of PHP functions in connecting to database

PHP provides a variety of functions for database connections: PDO connection: Use PDO::__construct() to establish a connection, and the PDO::ATTR_ERRMODE exception mode can catch errors. MySQLi connection: Establish a connection through mysqli_connect(). If the connection fails, use mysqli_connect_error() to output an error. Close the connection: Use PDO::close() or mysqli_close() to close the connection and release resources. Practical case: PDO connects to the database, executes the query, traverses the results and outputs the article title.

Application of PHP functions in database connections

PHP provides a wealth of functions to connect and manage database connections. These functions simplify the process of interacting with the database, allowing developers to easily access data from PHP applications.

PDO Connection:

Using PDO (PHP Data Objects) provides a standardized way to connect and operate different databases. PDO function PDO::__construct() is used to establish a database connection:

<?php
$servername = "localhost";
$username = "root";
$password = "password";
$dbname = "mydb";

try {
  $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
  // 设置 PDO 错误模式以抛出异常
  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  echo "数据库连接成功";
} catch(PDOException $e) {
  echo "数据库连接失败：" . $e->getMessage();
}
?>

MySQLi connection:

MySQLi provides another connection to the MySQL database Options. You can use the mysqli_connect() function to establish a connection:

<?php
$servername = "localhost";
$username = "root";
$password = "password";
$dbname = "mydb";

$conn = mysqli_connect($servername, $username, $password, $dbname);

if (!$conn) {
  die("数据库连接失败：" . mysqli_connect_error());
}
echo "数据库连接成功";
?>

Close the connection:

After performing the database operation, the connection must be closed to release resources. You can use the PDO::close() or mysqli_close() function to close the PDO or MySQLi connection:

<?php
// 使用 PDO
$conn->close();

// 使用 MySQLi
mysqli_close($conn);
?>

Practical case:

Consider a simple blogging application where we need to connect to a database and retrieve a list of post titles.

<?php
try {
  // 建立 PDO 连接
  $conn = new PDO("mysql:host=localhost;dbname=myblog", "root", "password");

  // 准备 SQL 查询
  $stmt = $conn->prepare("SELECT title FROM articles");

  // 执行查询
  $stmt->execute();

  // 获取结果
  $results = $stmt->fetchAll(PDO::FETCH_ASSOC);

  // 遍历结果并输出文章标题
  foreach ($results as $row) {
    echo $row['title'] . "<br>";
  }
} catch(PDOException $e) {
  echo "数据库操作失败：" . $e->getMessage();
}
?>

Through these functions, PHP developers can easily and efficiently connect and manage database connections, simplifying interaction with the database.

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