var arrayTopics = new Array();

function clickPost( topicId )
{
    imgElement = document.getElementById( 'img' + topicId );
    
    if ( arrayTopics[topicId] == true )
    {
        arrayTopics[topicId] = false;
        
        imgElement.src = imgOff;
    }
    else
    {
        arrayTopics[topicId] = true;
        
        imgElement.src = imgOn;
    }
}