wikimedia / mediawiki

		# Initial colon indicates main namespace rather than specified default

		# but should not create invalid {ns,title} pairs such as {0,Project:Foo}

		if ( $dbkey !== '' && ':' == $dbkey[0] ) {

			$parts['namespace'] = NS_MAIN;

			$dbkey = substr( $dbkey, 1 ); # remove the colon but continue processing

			$dbkey = trim( $dbkey, '_' ); # remove any subsequent whitespace

		}

		if ( $dbkey == '' ) {

			throw new MalformedTitleException( 'title-invalid-empty', $text );

					# If there's an initial colon after the interwiki, that also

					# resets the default namespace

					if ( $dbkey !== '' && $dbkey[0] == ':' ) {

						$parts['namespace'] = NS_MAIN;

						$dbkey = substr( $dbkey, 1 );

					}

				}

				# If there's no recognized interwiki or namespace,

				# then let the colon expression be part of the title.