Redeclare issue user_has_role following upgrade from Drupal 7.34 to Drupal 7.36
The user_has_role() function has been introduced with Drupal 7.36, as stated here, and detailed here.

Following information given by the error message you received we see that:


the function is primarily declared in modules/user/user.module:863: looking at the code of the user module confirm this, ok
the new declaration is said to happen through modules/php/php.module(80): again, looking at the code of the php module confirms that line 80 executes eval('?&gt; . $code);, ok
so the culpry supplemental declaration should be found at line 23 of the PHP content of a field which uses a format where the (not so usual) PHP evaluator filter has been enabled


IMO you should:


review all of your defined text formats, in order to select which of them have PHP evaluator filter enabled
from this reduced list, look for any node or block using these text formats (should not be as many)
then review the corresponding contents, where you'll probably find that somebody had created its own user_has_role() function for its needs, since it didn't exist yet before 7.36


HTH