set_url_scheme() │ WP 3.4.0

Sets the scheme for a URL.

Uses: is_ssl(), force_ssl_admin()
1 time — 0.000017 sec (very fast) | 50000 times — 0.07 sec (speed of light) | PHP 7.0.2, WP 4.4.1
Hooks from the function

Return

String. URL with chosen scheme.

Usage

set_url_scheme( $url, $scheme );
$url(string) (required)
Absolute URL that includes a scheme
$scheme(string|null)
Scheme to give $url. Currently 'http', 'https', 'login', 'login_post', 'admin', 'relative', 'rest', 'rpc', or null.
Default: null

Changelog

Since 3.4.0 Introduced.
Since 4.4.0 The 'rest' scheme was added.

Code of set_url_scheme() WP 6.0

wp-includes/link-template.php 
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 ( substr( $url, 0, 2 ) === '//' ) {
		$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 );
}

ssl

Formatting