If you've published/uploaded your form to your server and are testing it, you might see an error that looks similar to this when clicking the submit button:
Parse error: syntax error, unexpected T_OBJECT_OPERATOR in /home/content/w/f/p/wfp78207/html/temp/emailform/emailform/fbapp/php/formpage.cls.php on line 475
This means that your server does not meet the minimum server requirements. Most likely, your server is using an older version of PHP. You must have PHP 5.2 or higher installed. Contact your server administrator and ask them to update to the most recent version of PHP.
You can read more about minimum server requirements here.