Regular expression to get the classes: 'class="[^"]'

Function to replace classes:

function replaceClasses($classAttribute)
{
    $classes = explode(' ', $classAttribute);

    if(in_array('active', $classes)
    {
        return 'active';
    }
    else if(in_array('parent', $classes))
    {
        return 'parent';
    }
    else
    {
        return $classAttribute;
    }
}