wp_set_post_tags() │ WP 2.3.0

Set the tags for a post.

No Hooks.

Array|false|WP_Error. Array of term taxonomy IDs of affected terms. WP_Error or false on failure.

wp_set_post_tags( $post_id, $tags, $append );

$post_id(int): The Post ID. Does not default to the ID of the global $post.
$tags(string|array): An array of tags to set for the post, or a string of tags separated by commas.
Default: ''
$append(true|false): If true, don't delete existing tags, just add on. If false, replace the tags with the new tags.
Default: false

This example adds post 42 to the "feelings" and "life" tags (current post tags remains). If the specified tags do not exist, they will be created:

wp_set_post_tags( 42, 'feelings,life', true );

Current post tags will be unset and specified ones will be set.

$post_id = 100;
$tags = [ 'Mango', 'Apple', 'Banana' ];

wp_set_post_tags( $post_id, $tags );

Since 2.3.0

Introduced.

function wp_set_post_tags( $post_id = 0, $tags = '', $append = false ) {
	return wp_set_post_terms( $post_id, $tags, 'post_tag', $append );
}