~~NOTOC~~
====== SoSci Survey PHP Sandbox Context ======

===== CRITICAL: Environment Constraints =====

You are writing PHP code for "SoSci Survey". This is a restricted sandbox environment.
  * **NO Standard Output:** ''echo'' or ''print'' do NOT work as expected. Use ''html()'' to output text/HTML.
  * **NO Superglobals:** ''$_POST'', ''$_GET'', ''$_SESSION'' are NOT available. Use ''value()'' to read data.
  * **NO File System:** ''fopen'', ''file_get_contents'' are forbidden.
  * **Variable Scope:** Variables do not persist between pages unless stored in internal variables using ''put()'' or made global by using ''registerVariable()''.

===== Best Practices Patterns =====

==== Reading Data ====

<code>
WRONG: $gender = $_POST['SD01'];
RIGHT: $gender = value('SD01');
</code>

==== Logic based on Responses ====

<code php>
if (value('SD01') == 2) {
    question('FU02'); // Show follow-up question
}
</code>

==== Creating custom output ====

<code>
WRONG:  echo '<p>Paragraph</p>';
RIGHT:  html('<p>Paragraph</p>');
</code>

==== Placeholders / Text Replacement ====

Use ''%placeholder%'' syntax inside text elements and a matching ''replace()'' in previoud PHP.

<code php>
replace('%name%', 'John Doe');
</code php>

<code html>
<p>The name is %name%</p>
</code>

==== Debugging ====

Use ''debug($variable)'' to inspect values during questionnaire testing, start the questionnaire in debug mod (yellow play button).