PHP에서 데이터베이스 선택이 미치는 영향에 대한 심층 분석

<?php

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

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

// 检测连接
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

// 查询数据
$sql = "SELECT id, name, email FROM users";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Email: " . $row["email"]. "<br>";
    }
} else {
    echo "0 results";
}

// 关闭连接
mysqli_close($conn);

?>

<?php

$db = new SQLite3('test.db');

// 查询数据
$results = $db->query('SELECT * FROM users');

while ($row = $results->fetchArray()) {
    var_dump($row);
}

// 关闭连接
$db->close();

?>

<?php

$dbconn = pg_connect("host=localhost dbname=dbname user=username password=password");

// 查询数据
$result = pg_query($dbconn, "SELECT id, name, email FROM users");
if (!$result) {
    echo "Query failed.";
    exit;
}

while ($row = pg_fetch_row($result)) {
    echo "id: $row[0] - Name: $row[1] - Email: $row[2]<br>";
}

// 关闭连接
pg_close($dbconn);

?>