====== dropValue() ======

''void**dropValue**(String //variableID//)''

The function ''dropValue()'' deletes the current value of a variable with the specified //variableID//.

  * //variableID//\\ The variable identification as specified in the **variables overview**.

**Caveat:** A value deleted by means of ''dropValue()'' cannot be restored. In the data set the variable apears to be missing as if it had not been levied.


===== Applications =====

The function ''dropValue()'' can be useful in levying the e-mail address of an individual in order to send an e-mail to that address via ''[[:en:create:functions:mailsend]]'' and then delete the e-mail address afterwards. However, if the e-mail is not to include user specific information, the function [[en:create:questions:email]] may be more useful.

Anotoher application may arise if an interviewee is to provide an answer (e.g. an e-mail address or a short essay) which is not to be saved in the data set due to privacy issues. This may be needed as a priming task or if the interviewer is only interested in the length of the text entered, but not its actual content. However, if you do save information on the text entered, please consider that PHP-code may be executed repeatedly - e.g. if the interviewee reloads the page. In such cases the function ''[[:de:create:functions:getroute]]'' may be helpful. Also note, that the interviewee should not be provided a button to go back. 

<code php>
if (getRoute() == 'next') {
  // determines length of the entered text TX01_01 (in characters)
  $length = mb_strlen(value('TX01_01'));
  // saves the length in the internal variable IV01_01 
  put('IV01_01', $length);
  // deletes the actual text that was entered 
  dropValue('TX01_01');
}
</code>