Cannot set variable within IF Statement for some reason

Really not sure what's going on here, but this just isn't working! Anyone have any ideas on this?

I've tried this:

if(article_custom_field('product-type') !== '') {
    if(article_custom_field('product-type') == 'cd') return $productType = 'cd'; 
    if(article_custom_field('product-type') == 'audio') return $productType = 'headphones'; 
    if(article_custom_field('product-type') == 'video') return $productType = 'facetime-video'; 
    if(article_custom_field('product-type') == 'download') return $productType = 'save'; 
    if(article_custom_field('product-type') == 'book') return $productType = 'book'; 

} else {
    $productType = 'eye-open';
}

And this:

if(article_custom_field('product-type') === 'cd') {
    $productType = 'cd';
} elseif(article_custom_field('product-type') === 'video') {
    $productType = 'facetime-video';
} elseif(article_custom_field('product-type') === 'audio') {
    $productType = 'headphones';
} elseif(article_custom_field('product-type') === 'download') {
    $productType = 'save';
} elseif(article_custom_field('product-type') === 'book') {
    $productType = 'book';
} else {
    $productType = 'eye-open';
}

The aim to to change this:

                                    <span class="product-type">
                                    <img src="<?php echo theme_url('/assets/glyphicon-' . $productType . '.png'); ?>" width="25" alt="Product Type" class="img-responsive">
                                    <?php echo article_custom_field('product-type'); ?>
                                </span>

Any ideas as to what I am doing wrong and why this code just isn't working for me? Whatever I set the 'article_custom_field('product-type') to, I still get 'eye-open'. What's the deal?