====== serialCheck() ======

''int **serialCheck**(string //authorizationCode//)''

The function ''serialCheck()'' reveals whether an //authorizationCode//  is valid, and whether it has already been used. This function can be helpful in calling up an authorization code manually.

**Note:** Only the status of an authorization code can be checked with this function -- the authorization code will not be marked as "used" at the end of the questionnaire.


===== Return Value =====

''serialCheck()'' generates one of the following codes:

^Code^Meaning^
|-1|No authorization code specified|
|0|Authorization code not recognized in the survey project|
|1|Authorization code already used (questionnaire is thus completed)|
|2|Questionnaire was already called up with the authorization code, but not completed|
|3|Authorization code yet to be used|


===== Example =====

The following example assumes that an authorization code was asked for on the previous page in the text input field "AB01_01". The PHP code now checks whether the authorization code specified is valid. If not, the PHP code shows a text element as an error message, and redisplays the previous page with ''[[:en:create:functions:repeatpage|repeatPage]]'' 

<code php>
$serial = value('AB01_01');
$status = serialCheck($serial);

if ($status == -1) {
  repeatPage('serialVoid');
} elseif ($status == 0) {
  repeatPage('serialWrong');
} elseif ($status == 1) {
  repeatPage('serialUsed');
}
</code>