Using the *first* Image as Featured Image

So you have this function which is supposed to use the first image in an “image”-post automagically as featured image. But it doesn’t. It uses the last image.

I hacked the functions.php to be sure to use the first image.

In your functions.php find the line where it says
function pinboard_get_first_image() {

Replace the whole function (until the closing “}” briefly before the “endif;”-tag) with:

function pinboard_get_first_image() {
	$document = new DOMDocument();
	$content = apply_filters( 'the_content', get_the_content( '', true ) );
	if( '' != $content ) {
		libxml_use_internal_errors( true );
		$document->loadHTML( $content );
		libxml_clear_errors();
		$images = $document->getElementsByTagName( 'img' );
		$document = new DOMDocument();
		$images_amount = ($images->length); // How many images are there in the post?
		if( $images->length ) {
			$image= $images->item( $images->length - $images_amount ); // The first image ist the 0 (zero).
			$src = $image->getAttribute( 'src' );
			$width = ( $image->hasAttribute( 'width' ) ? $image->getAttribute( 'width' ) : false );
			$height = ( $image->hasAttribute( 'height' ) ? $image->getAttribute( 'height' ) : false );
			return array( $src, $width, $height );
		}
	}
	return false;
}

The changes I made are concerning the variable $images_amount.