wp-includes/link-template.php:3930Sets the scheme for a URL.
$urlstring$schemestring|nulloptionalnullstringOne hook fires while set_url_scheme() runs, in this order:
Filters the resulting URL after setting the scheme.
function set_url_scheme( $url, $scheme = null ) { $orig_scheme = $scheme; if ( ! $scheme ) { $scheme = is_ssl() ? 'https' : 'http'; } elseif ( 'admin' === $scheme || 'login' === $scheme || 'login_post' === $scheme || 'rpc' === $scheme ) { $scheme = is_ssl() || force_ssl_admin() ? 'https' : 'http'; } elseif ( 'http' !== $scheme && 'https' !== $scheme && 'relative' !== $scheme ) { $scheme = is_ssl() ? 'https' : 'http'; } $url = trim( $url ); if ( str_starts_with( $url, '//' ) ) { $url = 'http:' . $url; } if ( 'relative' === $scheme ) { $url = ltrim( preg_replace( '#^\w+://[^/]*#', '', $url ) ); if ( '' !== $url && '/' === $url[0] ) { $url = '/' . ltrim( $url, "/ \t\n\r\0\x0B" ); } } else { $url = preg_replace( '#^\w+://#', $scheme . '://', $url ); } /** * Filters the resulting URL after setting the scheme. * * @since 3.4.0 * * @param string $url The complete URL including scheme and path. * @param string $scheme Scheme applied to the URL. One of 'http', 'https', or 'relative'. * @param string|null $orig_scheme Scheme requested for the URL. One of 'http', 'https', 'login', * 'login_post', 'admin', 'relative', 'rest', 'rpc', or null. */ return apply_filters( 'set_url_scheme', $url, $scheme, $orig_scheme );}Introduced in 3.4.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/link-template.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.