O clássico

Essa você já conhece, né?

<!-- Arquivo: index.html -->
<!DOCTYPE html>

<html>

<head>
    <title>Find user | TestSite</title>
    <meta charset="utf-8" />
</head>

<body lang="en-US">
    <h1>Find users</h1>
    <form method="GET" action="./user.php">
        <p>
            <label for="email">E-mail:</label>
            <input
                type="text"
                id="email"
                name="email"
                placehoder="user@example.com"
            />
        </p>

        <input type="submit" value="Open profile" />
    </form>
</body>

</html>

<?php

// Arquivo: user.php

$dbHost = getenv('DB_HOST');
$dbName = getenv('DB_NAME');
$dbUser = getenv('DB_USER');
$dbPass = getenv('DB_PASS');
$dbCharset = getenv('DB_CHARSET') ?: 'utf8mb4';

try {
    $pdo = new PDO(
        "mysql:host=$dbHost;dbname=$dbName;charset=$dbCharset",
        $dbUser,
        $dbPass,
    );

    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    $email = $_GET['email'];

    $sql = "
        SELECT
            email,
            name
        FROM users
        WHERE
            email = '$email'
    ";

    $statement = $pdo->prepare($sql);
    $statement->execute();

    $users = $statement->fetchAll(PDO::FETCH_ASSOC);
} catch (\Throwable $e) {
    throw $e;
    echo "Something went wrong!";

    http_response_code(500);
    return;
}

foreach ($users as $user) {
    echo "Name: {$user['name']} | E-mail: {$user['email']}<br />";
}