wp_match_mime_types() WordPress Function

function wp_match_mime_types( $wildcard_mime_types, $real_mime_types ) {
	$matches = array();
	if ( is_string( $wildcard_mime_types ) ) {
		$wildcard_mime_types = array_map( 'trim', explode( ',', $wildcard_mime_types ) );
	}
	if ( is_string( $real_mime_types ) ) {
		$real_mime_types = array_map( 'trim', explode( ',', $real_mime_types ) );
	}

	$patternses = array();
	$wild       = '[-._a-z0-9]*';

	foreach ( (array) $wildcard_mime_types as $type ) {
		$mimes = array_map( 'trim', explode( ',', $type ) );
		foreach ( $mimes as $mime ) {
			$regex = str_replace( '__wildcard__', $wild, preg_quote( str_replace( '*', '__wildcard__', $mime ) ) );

			$patternses[][ $type ] = "^$regex$";

			if ( false === strpos( $mime, '/' ) ) {
				$patternses[][ $type ] = "^$regex/";
				$patternses[][ $type ] = $regex;
			}
		}
	}
	asort( $patternses );

	foreach ( $patternses as $patterns ) {
		foreach ( $patterns as $type => $pattern ) {
			foreach ( (array) $real_mime_types as $real ) {
				if ( preg_match( "#$pattern#", $real )
					&& ( empty( $matches[ $type ] ) || false === array_search( $real, $matches[ $type ], true ) )
				) {
					$matches[ $type ][] = $real;
				}
			}
		}
	}

	return $matches;
}