get_custom_logo( int $blog_id = 0 ): string

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$blog_idintoptional

ID of the blog in question. Default is the ID of the current blog.Default: 0

Return value

string

Custom logo markup.

Performance profile

How much work a call to get_custom_logo() 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

Heavy

Reaches the database via get_post().

Scaling

Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions

19–116

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 139.

Plugin surface

2 hooks

Third-party callbacks on 'get_custom_logo_image_attributes', 'get_custom_logo' run inside this call, and their cost is not bounded by anything here.

Called by

4

4 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• hookthird-party callbacksapply_filters()called directly
• optionoption read or writeget_option()called directly
• cacheobject cachewp_cache_switch_to_blog()one call below get_custom_logo()
• querycontent queryget_post()one call below get_custom_logo()
• serializeserialisationmaybe_unserialize()one call below get_custom_logo()

Further down the call graph this can also reach transient. That is the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 600 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost get_custom_logo() can have, taken from its control-flow graph on PHP 8.5.

Hooks and filters fired · 2

2 hooks fire while get_custom_logo() runs, in this order:

1. 1
   apply_filters( get_custom_logo_image_attributes )filterline 1103 (+45 into the body)

   Filters the list of custom logo image attributes.

2. 2
   apply_filters( get_custom_logo )filterline 1152 (+94 into the body)

   Filters the custom logo output.

Uses · 19

• is_multisite()Determines whether Multisite is enabled.
• get_current_blog_id()Retrieves the current site ID.
• switch_to_blog()Switches the current blog.
• has_custom_logo()Determines whether the site has a custom logo.
• get_theme_mod()Retrieves theme modification value for the active theme.
• get_theme_support()Gets the theme support arguments passed when registering that support.
• is_front_page()Determines whether the query is for the front page of the site.
• is_paged()Determines whether the query is for a paged result and not for the first page.
• get_post_meta()Retrieves a post meta field for the given post ID.
• get_bloginfo()Retrieves information about the current site.
• apply_filters()Calls the callback functions that have been added to a filter hook.
• wp_get_attachment_image()Gets an HTML img element representing an image attachment.

Used by · 4

• WP_Customize_Manager::_render_custom_logo_partial()Callback for rendering the custom logo, used in the custom_logo partial.
• render_block_core_site_logo()Renders the `core/site-logo` block on the server.
• the_custom_logo()Displays a custom logo, linked to home unless the theme supports removing the link on the home page.
• twentytwenty_site_logo()Displays the site logo, either text or image.

Source code

View on Trac ↗View on GitHub ↗

1058function get_custom_logo( $blog_id = 0 ) {1059	$html          = '';1060	$switched_blog = false;1061 1062	if ( is_multisite() && ! empty( $blog_id ) && get_current_blog_id() !== (int) $blog_id ) {1063		switch_to_blog( $blog_id );1064		$switched_blog = true;1065	}1066 1067	// We have a logo. Logo is go.1068	if ( has_custom_logo() ) {1069		$custom_logo_id   = get_theme_mod( 'custom_logo' );1070		$custom_logo_attr = array(1071			'class'   => 'custom-logo',1072			'loading' => false,1073		);1074 1075		$unlink_homepage_logo = (bool) get_theme_support( 'custom-logo', 'unlink-homepage-logo' );1076 1077		if ( $unlink_homepage_logo && is_front_page() && ! is_paged() ) {1078			/*1079			 * If on the home page, set the logo alt attribute to an empty string,1080			 * as the image is decorative and doesn't need its purpose to be described.1081			 */1082			$custom_logo_attr['alt'] = '';1083		} else {1084			/*1085			 * If the logo alt attribute is empty, get the site title and explicitly pass it1086			 * to the attributes used by wp_get_attachment_image().1087			 */1088			$image_alt = get_post_meta( $custom_logo_id, '_wp_attachment_image_alt', true );1089			if ( empty( $image_alt ) ) {1090				$custom_logo_attr['alt'] = get_bloginfo( 'name', 'display' );1091			}1092		}1093 1094		/**1095		 * Filters the list of custom logo image attributes.1096		 *1097		 * @since 5.5.01098		 *1099		 * @param array $custom_logo_attr Custom logo image attributes.1100		 * @param int   $custom_logo_id   Custom logo attachment ID.1101		 * @param int   $blog_id          ID of the blog to get the custom logo for.1102		 */1103		$custom_logo_attr = apply_filters( 'get_custom_logo_image_attributes', $custom_logo_attr, $custom_logo_id, $blog_id );1104 1105		/*1106		 * If the alt attribute is not empty, there's no need to explicitly pass it1107		 * because wp_get_attachment_image() already adds the alt attribute.1108		 */1109		$image = wp_get_attachment_image( $custom_logo_id, 'full', false, $custom_logo_attr );1110 1111		// Check that we have a proper HTML img element.1112		if ( $image ) {1113 1114			if ( $unlink_homepage_logo && is_front_page() && ! is_paged() ) {1115				// If on the home page, don't link the logo to home.1116				$html = sprintf(1117					'<span class="custom-logo-link">%1$s</span>',1118					$image1119				);1120			} else {1121				$aria_current = ! is_paged() && ( is_front_page() || is_home() && ( (int) get_option( 'page_for_posts' ) !== get_queried_object_id() ) ) ? ' aria-current="page"' : '';1122 1123				$html = sprintf(1124					'<a href="%1$s" class="custom-logo-link" rel="home"%2$s>%3$s</a>',1125					esc_url( home_url( '/' ) ),1126					$aria_current,1127					$image1128				);1129			}1130		}1131	} elseif ( is_customize_preview() ) {1132		// If no logo is set but we're in the Customizer, leave a placeholder (needed for the live preview).1133		$html = sprintf(1134			'<a href="%1$s" class="custom-logo-link" style="display:none;"><img class="custom-logo" alt="" /></a>',1135			esc_url( home_url( '/' ) )1136		);1137	}

Changelog

Introduced in 4.5.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

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