Check if the current post has any of the given tags. The given tags are checked against the post's tags' term_ids, names and slugs. Tags given as integers will only be checked against the post's tags' term_ids.
If no tags are given, determines if post has any tags.
Note: This function is mask of:
has_term( $tag, 'post_tag', $post )
Therefore if you are attempting to determine if a post of a custom post type has a particular tag you need to do:
has_term( $tag, 'mycpt_tag', $post )
<?php has_tag( $tag, $post ); ?>
has_tag() is located in