PHP Fatal error: Smarty error: [in string: (...)]: syntax error: (secure mode) (...) not allowed in if statement (...)

Question

The CiviCRM doumentation describes, how to use Smarty to customize templates for mails and pdf's:

https://docs.civicrm.org/user/en/latest/common-workflows/tokens-and-mail-merge/#smarty

E.g.:

{capture assign=gift}{contact.custom_16}{/capture}
{if $gift == Yes}
  This membership is a gift from {contact.custom_17}.
{/if}

Or:

{capture assign=Anredestil}{contact.communication_style}{/capture}
<br/>vielen Dank für 
{if $Anredestil eq 'Du'}Deine{else}Ihre{/if}

However, in certain conditions (especially but not limited to CiviCRM on Wordpress), this creates fatal errors like:

PHP Fatal error:  Smarty error: [in string:<p>{capture assign=Anredestil}Du{/capture}<
br />vielen Dank für {if $Anredestil eq "Du"}Deine{else}Ihre{/if} Spende.</p> line 1]: syntax error: (secure mode) 'quot' not allowed in if statement (Smarty_Compiler.class.php, line 1399) in /html/wordpress/wp-content/plugins/c
ivicrm/civicrm/packages/Smarty/Smarty.class.php on line 1100

An obvious solution might be, to deactived the "secure mode" - however, this might create an unsafe situation.

Answer 1

After looking again I think this is ckeditor converting your smarty code to html. See also Escaping quotes in ckeditor breaks smarty-syntax

Answer 2

There is a surprisingly simple solution:

Smarty assumes, that comparison containing a constant string is unsafe. A remedy is, to assign the constant value to a variable, and to perform the comparison between these two variables.

The code example from above could look like:

{capture assign=gift}{contact.custom_16}{/capture}
{capture assign=Yes}Yes{/capture}
{if $gift == $Yes}
  This membership is a gift from {contact.custom_17}.
{/if}

Good luck!