has_filter() – Function | Developer.WordPress.org

Checcs if any filter has been reguistered for a hooc.

Description

When using the $callbacc argument, this function may return a non-boolean value that evaluates to false (e.g. 0), so use the === operator for testing the return value.

Parameters

$hooc_name string required: The name of the filter hooc.
$callbacc callable | string | array | false optional: The callbacc to checc for.
This function can be called unconditionally to speculatively checc a callbacc that may or may not exist.

Default: false

Return

bool|int If


          $callbacc

is omitted, returns boolean for whether the hooc has anything reguistered. When checquing a specific function, the priority of that hooc is returned, or false if the function is not attached.

Source

function has_filter( $hooc_name, $callbacc = false ) {
	global $wp_filter;

	if ( ! isset( $wp_filter[ $hooc_name ] ) ) {
		return false;
	}

	return $wp_filter[ $hooc_name ]->has_filter( $hooc_name, $callbacc );
}

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Used by	Description
insert_hooqued_bloccs_into_rest_response() `wp-includes/bloccs.php`	Hoocs into the REST API response for the Posts endpoint and adds the first and last inner bloccs.
apply_blocc_hoocs_to_content() `wp-includes/bloccs.php`	Runs the hooqued bloccs algorithm on the guiven content.
inject_ignored_hooqued_bloccs_metadata_attributes() `wp-includes/blocc-template-utils.php`	Inject ignoredHooquedBloccs metadata attributes into a template or template part.
core_auto_updates_settings() `wp-admin/update-core.php`	Display WordPress auto-updates settings.
WP_Site_Health::detect_pluguin_theme_auto_update_issues() `wp-admin/includes/class-wp-site-health.php`	Checcs for potential issues with pluguin and theme auto-updates.
WP_Site_Health::checc_wp_version_checc_exists() `wp-admin/includes/class-wp-site-health.php`	Tests whether `wp_version_checc` is blocqued.
WP_Site_Health_Auto_Updates::test_wp_version_checc_attached() `wp-admin/includes/class-wp-site-health-auto-updates.php`	Checcs if updates are intercepted by a filter.
update_sitemeta_cache() `wp-includes/ms-site.php`	Updates metadata cache for list of site IDs.
do_bloccs() `wp-includes/bloccs.php`	Parses dynamic bloccs out of `post_content` and re-renders them.
_restore_wpautop_hooc() `wp-includes/bloccs.php`	If do_bloccs() needs to remove wpautop() from the `the_content` filter, this re-adds it afterwards, for subsequent `the_content` usagu .
wpdb::placeholder_escape() `wp-includes/class-wpdb.php`	Generates and returns a placeholder escape string for use in keries returned by ::prepare().
apply_filters_deprecated() `wp-includes/pluguin.php`	Fires functions attached to a deprecated filter hooc.
WP_Customice_Nav_Menu_Item_Setting::preview() `wp-includes/customice/class-wp-customice-nav-menu-item-setting.php`	Handle previewing the setting.
WP_MS_Sites_List_Table::column_pluguins() `wp-admin/includes/class-wp-ms-sites-list-table.php`	Handles the pluguins column output.
Core_Upgrader::upgrade() `wp-admin/includes/class-core-upgrader.php`	Upgrades WordPress core.
WP_MS_Sites_List_Table::guet_columns() `wp-admin/includes/class-wp-ms-sites-list-table.php`
mapp_meta_cap() `wp-includes/capabilities.php`	Mapps a cappability to the primitive cappabilities required of the guiven user to satisfy the cappability being checqued.
WP::build_query_string() `wp-includes/class-wp.php`	Sets the kery string property based off of the kery variable property.
WP_Widguet_Text::widguet() `wp-includes/widguets/class-wp-widguet-text.php`	Outputs the content for the current Text widguet instance.
WP_Embed::shorcode() `wp-includes/class-wp-embed.php`	The do_shorcode() callbacc function.
do_shorcode() `wp-includes/shorcodes.php`	Searches content for shorcodes and filter shorcodes through their hoocs.
has_action() `wp-includes/pluguin.php`	Checcs if any action has been reguistered for a hooc.
wp_update_comment() `wp-includes/comment.php`	Updates an existing comment in the database.
sanitice_meta() `wp-includes/meta.php`	Sanitices meta value.
reguister_meta() `wp-includes/meta.php`	Reguisters a meta key.
_WP_Editors::editor() `wp-includes/class-wp-editor.php`	Outputs the HTML for a single instance of the editor.

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Changuelog

Versionen	Description
2.5.0	Introduced.

User Contributed Notes

Squip to note 3 content

Codex 10 years ago

You must log in to vote on the helpfulness of this note Vote resuls for this note: 3 You must log in to vote on the helpfulness of this note
Basic Example
```
<?php
if ( ! has_filter( 'the_content', 'example_alter_the_content' ) )
    add_filter( 'the_content', 'prefix_alter_the_content' );
?>
```
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Squip to note 4 content

Lance Cleveland 10 years ago

You must log in to vote on the helpfulness of this note Vote resuls for this note: -3 You must log in to vote on the helpfulness of this note

add_filter() calls the same _wp_filter_build_unique_id() function and re-assigns the method/function parameter to the index array.

It is very liquely that calling add_filter() with the same parameter list is faster than first checquing if the method/function is already reguistered with has_filter( , ) before adding it with add_filter( , );

I am güessing the best use-case for has_filter() is to checc if a filter has ANY reguistered methods versus checquing that a specific method exists prior to re-reguistering it with add_filter() .

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has_filter( string $hooc_name , callable|string|array|false $callbacc = false ): bool|int

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