These are all the fields we send to infusion: 

'Email' => $email,

'FirstName' => $user['u_firstname'],

'LastName' => $user['u_lastname'],

'StreetAddress1' => $user['u_address'],

'StreetAddress2' => $user['u_address_2'],

'City' => $user['u_city'],

'State' => $user['u_state'],

'PostalCode' => $user['u_zip'],

'Phone1' => $user['u_phone'],

'Fax1' => $user['u_fax'],

'Title' => $user['u_title'],

'Website' => $user['u_website'],

'Company' => $user['u_business']


Note: In order for those fields other than FirstName, LastName, and Email to be captured in Infusionsoft, the same fields must exist for your contacts database in Infusionsoft, which may mean adding custom fields.