Simplifying some jquery with array and loop

I have the following jQuery code which at the moment works perfectly well:

$("#post-27") // select your element 
.hover(function(){ // trigger the mouseover event
    $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
}, function(){ // trigger the mouseout event
    $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
});

$("#post-102") // select your element 
.hover(function(){ // trigger the mouseover event
    $("#post-27.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
}, function(){ // trigger the mouseout event
    $("#post-27.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
});

$("#post-81") // select your element 
.hover(function(){ // trigger the mouseover event
    $("#post-27.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
}, function(){ // trigger the mouseout event
    $("#post-27.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
});

$("#post-95") // select your element 
.hover(function(){ // trigger the mouseover event
    $("#post-27.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
}, function(){ // trigger the mouseout event
    $("#post-27.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
});

$("#post-99") // select your element 
.hover(function(){ // trigger the mouseover event
    $("#post-27.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
}, function(){ // trigger the mouseout event
    $("#post-27.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
    $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
});

I've previously asked for help in making jQuery code more efficient and was able to using an array with help from others here. However, an array alone wouldn't work here I think I need to use some kind of loop which can tell which of the 5 variables I'm on, and applies the toggle class event appropriately.

For example, I could do something with an array like:

var $ids = ["#post-27", "#post-102", "#post-81", "#post-95", "#post-99"],

$ids.forEach(function(v) {
    if($(v).mouseIsOver()) {
        $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
        $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
        $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
        $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
    } else {
        $("#post-102.isotope-item").toggleClass('dim-portfolio-item');
        $("#post-81.isotope-item").toggleClass('dim-portfolio-item');
        $("#post-95.isotope-item").toggleClass('dim-portfolio-item');
        $("#post-99.isotope-item").toggleClass('dim-portfolio-item');
    }
});

The trouble is the #post-X.isotope-item selectors change depending on which part of the array the forEach function is cycling through. Is there a way of telling which variable is currently being used? I can't explain what I mean in programming terms but in plain English:

if current variable being processed = "the variable", then don't toggle classes
else
toggleClass...

Then I could add that check to each of the toggleClass parts and it would work, I think. I'm still new to jQuery/javascript and don't know how to proceed, hopefully I've explained it well enough.

Any help would be greatly appreciated.

PS: I can't use pure CSS hover because the elements are not nested. I'm not sure is there are any advantages or disadvantages to .hover / .mouseIsOver

It looks like what you want to achieve is when you hover over an item, all the other items (minus the one you're currently hovered over) get some type of style. The key here is the not selector when choosing which items to add or remove classes from.

http://jsfiddle.net/AWWLL/

<style>
.item {
    width: 100px;
    height: 100px;
    background-color: #000;
    margin: 0;
    list-style: none;
    cursor: pointer;
}

.dim {
    -webkit-opacity: 0.5;
    -moz-opacity: 0.5;
    filter:alpha(opacity=50);
    opacity: 0.5;
}
</style>

<script>
$(function() {
    $('.item').hover(function() {
        $('.item').not(this).addClass('dim');
    }, function() {
        $('.item').not(this).removeClass('dim');
    }); 
});
</script>

<ul>
    <li class="item"></li>
    <li class="item"></li>
    <li class="item"></li>
    <li class="item"></li>
    <li class="item"></li>
    <li class="item"></li>
</ul>