file1.php
require_once(ABSPATH.'wp-config.php' );
require_once(ABSPATH.'functions.php' );

$domain = $_SERVER['HTTP_HOST'];
$uri = parse_url($_SERVER['HTTP_REFERER']);
$r_domain = $uri['host'];

add_action( 'admin_post_table', 'table' );
function table() {
if( ! check_ajax_referer( 'nonce', 'securitycheck' ) ) {
   wp_send_json_error('Security check failed');
}
if( ! empty($_POST['submission']) ) {
   wp_send_json_error('Security check failed, regular form entries only!');
}
if ( $domain == $r_domain ) {
$conn = f_sqlConnect();
if ( !f_tableExists($conn, $table) ) {
  try {
    $sql = "CREATE TABLE $table (
        ID int NOT NULL AUTO_INCREMENT,
        PRIMARY KEY(ID),
        ip int NOT NULL
    )";

    $result = $conn->exec($sql);
    } catch(PDOException $e) {
        echo $e->getMessage();  //Remove or change message in production code
        echo "Create table error";
    }
}

functions.php
/*Connects to and selects the specified database with the specified user.*/
function f_sqlConnect() {
$host = DB_HOST;
$db = DB_NAME;
try {
    $conn = new PDO("mysql:host=$host;dbname=$db", DB_USER, DB_PASSWORD);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "Connected successfully";
}
    Catch(PDOException $e)
{
    echo "Connection failed: " . $e->getMessage();
}
}

/*Checks to see if the specified table exists and if it doesn't, creates it.*/
function f_tableExists($conn, $table) {
//$table = preg_replace('/[^da-z_]/i', '', $table);
// Try a select statement against the table
// Run it in try/catch in case PDO is in ERRMODE_EXCEPTION.
try {
    $query = "SELECT 1 FROM $table LIMIT 1";
    $result = $conn->exec($query);

} catch (Exception $e) {
    echo "We got an exception == table not found";
    return FALSE;
}
echo "Result is either boolean FALSE (no table found) or PDOStatement Object (table found)";
return $result !== FALSE;
}