path_is_absolute( string $path ): bool

2119function path_is_absolute( $path ) {2120	/*2121	 * Check to see if the path is a stream and check to see if its an actual2122	 * path or file as realpath() does not support stream wrappers.2123	 */2124	if ( wp_is_stream( $path ) && ( is_dir( $path ) || is_file( $path ) ) ) {2125		return true;2126	}2127 2128	/*2129	 * This is definitive if true but fails if $path does not exist or contains2130	 * a symbolic link.2131	 */2132	if ( realpath( $path ) === $path ) {2133		return true;2134	}2135 2136	if ( strlen( $path ) === 0 || '.' === $path[0] ) {2137		return false;2138	}2139 2140	// Windows allows absolute paths like this.2141	if ( preg_match( '#^[a-zA-Z]:\\\\#', $path ) ) {2142		return true;2143	}2144 2145	// A path starting with / or \ is absolute; anything else is relative.2146	return ( '/' === $path[0] || '\\' === $path[0] );2147}