apply_filters( 'admin_url', string $url, string $path, int|null $blog_id, string|null $scheme )
Filters the admin area URL.
Parameters
- $url
-  (string) The complete admin area URL including scheme and path. 
- $path
-  (string) Path relative to the admin area URL. Blank string if no path is specified. 
- $blog_id
-  (int|null) Site ID, or null for the current site. 
- $scheme
-  (string|null) The scheme to use. Accepts 'http', 'https', 'admin', or null. Default 'admin', which obeys force_ssl_admin() and is_ssl(). 
Source
Changelog
| Version | Description | 
|---|---|
| 5.8.0 | The $schemeparameter was added. | 
| 2.8.0 | Introduced. | 
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Licensed under the GNU GPLv2+ License.
    https://developer.wordpress.org/reference/hooks/admin_url