is_tag( int|string|int[]|string[] $tag = '' ): bool
- Since
- 2.3.0
- Source
wp-includes/query.php:300
Description
If the $tag parameter is specified, this function will additionally check if the query is for one of the tags specified.
For more information on this and similar theme functions, check out the https://developer.wordpress.org/themes/basics/conditional-tags/ Conditional Tags article in the Theme Developer Handbook.
Compatibility
- WordPress
- since 2.3.0
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
Parameters
$tagint|string|int[]|string[]optional- Tag ID, name, slug, or array of such to check against. Default empty.Default:
''
Return value
bool- Whether the query is for an existing tag archive page.
Performance profile
How much work a call to is_tag() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Trivial
- Scaling
- Constant
- Instructions
- 8–13
- Plugin surface
- None
- Called by
- 14
Touches nothing outside its own arguments.
No loop in the body: the same number of instructions runs whatever you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 17.
Nothing here hands control to plugin code.
14 places in core call this, so the cost is paid more often than your own code shows.
What it touches
- hookthird-party callbacks
do_action()one call below is_tag()
Further down the call graph this can also reach query, option, cache, serialize and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.
What one call costs · 2 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost is_tag() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
isset($wp_query) | 8 | ->is_tag() |
!isset($wp_query) | 13 | __(), _doing_it_wrong() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 17 instructions, 8–13 executed per call, 1 branch. The work does not change between versions.
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Uses · 2
- _doing_it_wrong()Marks something as being incorrectly called.
- __()Retrieves the translation of $text.
Used by · 14
- WP::handle_404()Set the Headers for 404, if nothing is found for requested URL.
- feed_links_extra()Displays the links to the extra feeds such as category feeds.
- get_body_class()Retrieves an array of the class names for the body element.
- get_the_archive_title()Retrieves the archive title based on the queried object.
- redirect_canonical()Redirects incoming links to the proper URL based on the site url.
- render_block_core_term_description()Renders the `core/term-description` block on the server.
- render_block_core_term_template()Renders the `core/term-template` block on the server.
- rest_get_queried_resource_route()Gets the REST route for the currently queried object.
- single_term_title()Displays or retrieves page title for taxonomy term archive.
- term_description()Retrieves term description.
- twentynineteen_get_the_archive_title()Filters the default archive titles.
- wp_get_document_title()Returns document title for the current page.
Show all 14
- wp_list_categories()Displays or retrieves the HTML list of categories.
- wp_title()Displays or retrieves page title for all areas of blog.
Source code
function is_tag( $tag = '' ) { global $wp_query; if ( ! isset( $wp_query ) ) { _doing_it_wrong( __FUNCTION__, __( 'Conditional query tags do not work before the query is run. Before then, they always return false.' ), '3.1.0' ); return false; } return $wp_query->is_tag( $tag );}Changelog
Introduced in 2.3.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 7.1.0 tag, from
src/wp-includes/query.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.