Настраиваем массив $db под свои данные и готово.

Код: 

<?php
$db['name'] = 'test_db';
$db['host'] = 'localhost';
$db['user'] = 'root';
$db['pass'] = '';

$connect = new PDO("mysql:host=" . $db['host'] . ";dbname=" . $db['name'], $db['user'], $db['pass']);
$getAllTableQuery = "SHOW TABLES";
$statement = $connect->prepare($getAllTableQuery);
$statement->execute();
$result = $statement->fetchAll();

if(isset($_POST['table'])) {
    $output = '';

    foreach($_POST["table"] as $table) {
        $showTableQuery = "SHOW CREATE TABLE " . $table;
        $statement = $connect->prepare($showTableQuery);
        $statement->execute();
        $showTableResult = $statement->fetchAll();
        foreach($showTableResult as $showTableRow) {
            $output .= "\n\n" . $showTableRow["Create Table"] . ";\n\n";
        }
        $selectQuery = "SELECT * FROM " . $table;
        $statement = $connect->prepare($selectQuery);
        $statement->execute();
        $totalRow = $statement->rowCount();
        for($count=0; $count < $totalRow; $count++)
        {
            $singleResult = $statement->fetch(PDO::FETCH_ASSOC);
            $tableColumnArray = array_keys($singleResult);
            $tableValueArray = array_values($singleResult);
            $output .= "\nINSERT INTO $table (";
            $output .= "" . implode(", ", $tableColumnArray) . ") VALUES (";
            $output .= "'" . implode("','", $tableValueArray) . "');\n";
        }
    }

    $fileName = 'database_backup_on_' . date('y-m-d') . '.sql';
    $fileHandle = fopen($fileName, 'w+');
    fwrite($fileHandle, $output);
    fclose($fileHandle);
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename=' . basename($fileName));
    header('Content-Transfer-Encoding: binary');
    header('Expires: 0');
    header('Cache-Control: must-revalidate');
    header('Pragma: public');
    header('Content-Length: ' . filesize($fileName));
    ob_clean();
    flush();
    readfile($fileName);
    unlink($fileName);
}
?>
<!DOCTYPE html>
<html>
<head>
    <title>Создать бекап базы</title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.0-beta1/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-giJF6kkoqNQ00vy+HMDP7azOuL0xtbfIcaT9wjKHr8RbDVddVHyTfAAsrekwKmP1" crossorigin="anonymous">
</head>
<body>
<br />
<div class="container">
    <div class="row">
        <h2 align="center">Создать бекап базы</h2>
        <br />
        <form method="post" id="export_form">
            <h3>Выберите таблицы для бекапа</h3>
            <?php
            foreach($result as $table)
            {
                ?>
                <div class="checkbox">
                    <label><input type="checkbox" class="checkbox_table" name="table[]" value="<?php echo $table["Tables_in_" . $db['name']]; ?>" /> <?php echo $table["Tables_in_" . $db['name']]; ?></label>
                </div>
                <?php
            }
            ?>
            <div class="form-group">
                <input type="submit" name="submit" id="submit" class="btn btn-info" value="Export" />
            </div>
        </form>
    </div>
</div>
</body>
</html>
<script>
    $(document).ready(function() {
        $('#submit').click(function() {
            var count = 0;
            $('.checkbox_table').each(function() {
                if($(this).is(':checked')) {
                    count = count + 1;
                }
            });
            if(count > 0) {
                $('#export_form').submit();
            } else {
                alert("Выберите как минимум одну таблицу для экспорта");
                return false;
            }
        });
    });
</script>