Tracking: Uses of {php} to remove from Smarty in order to allow upgrade to Smarty 3+

This is the complete list remaining (not including those in pending PRs)

• https://github.com/civicrm/civicrm-core/blob/master/templates/CRM/Contact/Form/Task/PDFLetterCommon.hlp#L27 (I think we can get the param directly in Smarty 3 or maybe it would be OK to hardcode docx and odt in here)
• https://github.com/civicrm/civicrm-core/blob/master/templates/CRM/Admin/Page/APIExplorer.js#L752 (APIv3 Explorer ouputs {php} when we have an array, but in Smarty 3 we can pass in the array, so this can be removed)
• https://github.com/civicrm/civicrm-core/blob/master/templates/CRM/Campaign/Page/Petition/SocialNetwork.drupal#L28
• https://github.com/civicrm/civicrm-core/blob/master/templates/CRM/common/accesskeys.hlp#L11 (Could maybe redo this in JS)
• https://github.com/civicrm/civicrm-core/blob/master/templates/CRM/ACL/Header.tpl#L17
• https://github.com/civicrm/civicrm-core/blob/master/xml/templates/civicrm_msg_template.tpl