$(document).ready(function() {

   var tagsElem = $("#tags");

   tagsElem.autocomplete({
        source : "search.php",
        search : function( event, ui ){
            if(check(response,tagsElem.val()))
              response[response.length]=tagsElem.val()
            tagsElem.autocomplete( "option", "source", response);
        },
        open: function( event, ui ) {
            if(check(response,tagsElem.val())){
            tagsElem.next().find('li:last a').append(' <span style="color:red;">new</span>');
            }
                   }
    });

    function check(arrayTag,value){
     for(i=0;i<len;i++){
        if( arrayTag[i]==value)
                return false
        }
        return true
    }

});