get_intermediate_image_sizes() │ WP 3.0.0

$sizes = get_intermediate_image_sizes();
print_r( $sizes );

/* We get:
Array
(
	[0] => thumbnail
	[1] => medium
	[2] => medium_large
	[3] => large
	[4] => shop_thumbnail
	[5] => shop_catalog
	[6] => shop_single
	[7] => post-thumbnail
)
*/

But in this case we don't see the data of each of the sizes, what width and height is set for it, whether the image is cropped or not...

Also, if for example in the media files for the size "Large" set zeros (0) for height and width, then technically this size is disabled - no thumbnail is created for it anymore, but this function will show it.

To solve all these problems, use wp_get_registered_image_subsizes(). see the following example.

WordPress doesn't have such a built-in function, but it's not hard to create it using this function:

/**
 * Gets information about all registered image sizes.
 * 
 * @global $_wp_additional_image_sizes
 * @uses   get_intermediate_image_sizes()
 * 
 * @param bool $unset_disabled Remove dimensions with 0 height and width from the list?
 * @return array Data of all sizes.
 */
function get_image_sizes( $unset_disabled = true ) {

	$sizes = array();
	$wais = wp_get_additional_image_sizes();

	foreach ( get_intermediate_image_sizes() as $_size ) {

		if ( in_array( $_size, [ 'thumbnail', 'medium', 'medium_large', 'large' ] ) ) {

			$sizes[ $_size ] = array(
				'width'  => get_option( "{$_size}_size_w" ),
				'height' => get_option( "{$_size}_size_h" ),
				'crop'   => (bool) get_option( "{$_size}_crop" ),
			);
		}
		elseif ( isset( $wais[$_size] ) ) {

			$sizes[ $_size ] = array(
				'width'  => $wais[ $_size ]['width'],
				'height' => $wais[ $_size ]['height'],
				'crop'   => $wais[ $_size ]['crop'],
			);
		}

		// size registered, but has 0 width and height
		if( 
			$unset_disabled && ( $sizes[ $_size ]['width'] == 0 ) 
			&& 
			( $sizes[ $_size ]['height'] == 0 ) 
		){
			unset( $sizes[ $_size ] );
		}

	}

	return $sizes;
}

By calling such a function we get:

print_r( get_image_sizes() );

/*
Array
(
	[thumbnail] => Array
		(
			[width] => 80
			[height] => 80
			[crop] => 1
		)

	[medium] => Array
		(
			[width] => 120
			[height] => 120
			[crop] => 
		)

)
*/

Now, with a function at hand that gets all the image sizes and their data, you can easily extend the functionality by writing functions to get individual data of a specified size.

/**
 * Gets data of a certain image size.
 *
 * @uses   get_image_sizes()
 * @param string $size Size name
 * @return bool|array $size Image size data or false if there is no such size.
 */
function get_image_size( $size ) {
	$sizes = get_image_sizes(0);

	return $sizes[ $size ] ?? false;
}

/**
 * Gets the width of a specific image size.
 *
 * @uses   get_image_size()
 * @param string $size Size name
 * @return bool|int Width or false if no size.
 */
function get_image_size_width( $size ) {

	if ( ! $size = get_image_size( $size ) )
		return false;

	return $size['width'] ?? false;
}

/**
 * Gets the height of a specific image size.
 *
 * @uses   get_image_size()
 * @param string $size Size name
 * @return bool|int Height or false if there is no size.
 */
function get_image_size_height( $size ) {

	if ( ! $size = get_image_size( $size ) )
		return false;

	return $size['height'] ?? false;
}

And now a demonstration of the functions created:

$medium_size = get_image_size('medium');

/* will return:
Array
(
	[width] => 120
	[height] => 120
	[crop] => 
)
*/

$medium_size_width = get_image_size_width('medium'); //> 120

$medium_size_height = get_image_size_height('medium'); //> 120