How do I add a default thumbnail to elseif when no get_field('photos'), and no post thumbnail exists?

Question

I am using advanced custom fields pro to display an image if the option exists. If the option does not exist then it will look for a post thumbnail. I already have this code and it's working however I want to add an option to display a default image from my images folder if both options do not exist.

Here's the working code I currently have:

<?php if(get_field('photos')): ?>
<div class="img"><?php echo '<a class="image" href="' . get_permalink() . '"><div class="img"><img src="' . $model_pic[0]['sizes']['models'] . '" /></div><div class="info"><h3>' . get_the_title() . '</h3></div> </a> ' ?></div>

<?php else: ?>

<?php $small_image_url = wp_get_attachment_image_src( get_post_thumbnail_id(), 'models'); ?>
<div class="img"><?php echo '<a class="image" href="' . get_permalink() . '"><div class="img"><img src="' . $small_image_url[0] . '"/></div><div class="info"><h3>' . get_the_title() . '</h3></div> </a> ' ?></div>

<?php endif; ?>

I want to add a third else statement to the code so it will display an image from my theme images folder if there is no post thumbnail set.

Something like this: (but this does not work)

<?php if(get_field('photos')): ?>
<div class="img"><?php echo '<a class="image" href="' . get_permalink() . '"><div class="img"><img src="' . $model_pic[0]['sizes']['models'] . '" /></div><div class="info"><h3>' . get_the_title() . '</h3></div> </a> ' ?></div>

<?php elseif ?>

<?php $small_image_url = wp_get_attachment_image_src( get_post_thumbnail_id(), 'models'); ?>
<div class="img"><?php echo '<a class="image" href="' . get_permalink() . '"><div class="img"><img src="' . $small_image_url[0] . '"/></div><div class="info"><h3>' . get_the_title() . '</h3></div> </a> ' ?></div>

<?php else: ?>

echo '<img src="' . get_bloginfo( 'stylesheet_directory' ) . '/images/thumbnail-default.jpg" />';

<?php endif; ?>

Answer 1

The function you are looking for is has_post_thumbnail()

With this function you can check, if a featured image has been attached to a post and perform the following code:

<?php if( get_field( 'photos' ) ): ?>
    <div class="img">
        <?php echo '<a class="image" href="' . get_permalink() . '"><div class="img"><img src="' . $model_pic[0]['sizes']['models'] . '" /></div><div class="info"><h3>' . get_the_title() . '</h3></div> </a> ' ?>
    </div>
<?php elseif( has_post_thumbnail() ): 
    $small_image_url = wp_get_attachment_image_src( get_post_thumbnail_id(), 'models'); ?>
    <div class="img"><?php echo '<a class="image" href="' . get_permalink() . '"><div class="img"><img src="' . $small_image_url[0] . '"/></div><div class="info"><h3>' . get_the_title() . '</h3></div> </a> ' ?></div>
<?php else: ?>
    <div class="img">
        <img src="<?php echo get_template_directory_uri(); ?>/images/default.png" alt="" />
    </div>
<?php endif; ?>