[jQuery] [autocomplete] JSON response

I am getting JSON response(string format) from the URL to which I am
sending request. I want to use the methods formatResult to format the
result.

$("#month").autocomplete("Search.php", {
     minChars: 0,
     max: 12,
     autoFill: true,
     mustMatch: true,
     matchContains: false,
     scrollHeight: 220,
     formatItem: function(data, i, total) {
     if ( data[0] == months[new Date().getMonth()] )
         return false;
         return data[0];
     }
});

Here, the Search.php will return a JSON (string format). But this
plugin is looking for "|" symbols in the Ajax response.

Where can I convert to a JSON object using eval and use it as a local
JSON data?