WordPress: If the post has several categories, display the first one only.

category.php

<?php
	$category = get_the_category( get_the_ID() );
	if ( $category ) :
?>
	<span class="entry-category">
		<a href="<?php echo esc_url( get_category_link( $category[0]->term_id ) ); ?>"><?php echo esc_attr( $category[0]->name ); ?></a>
	</span>
<?php endif; // End if category ?>