I have the following function to get all of the different types of end-of-line delimiters in a file. There may be one or more, so I want to return an array of all types.

function ddtt_get_file_eol( $file_contents, $incl_code = true ) {
    $types = [
        'rn',
        'n',
        'r'
    ];
    $found = [];
    foreach ( $types as $type ) {
        if ( $type == 'rn' ) {
            $regex = "/rn/";
        } elseif ( $type == 'n' ) {
            $regex = "/(?<!r)n/";
        } else {
            $regex = "/r(?!n)/";
        }
        if ( preg_match( $regex, $file_contents ) ) {
            $found[] = ( $incl_code ) ? '<code class="hl">'.$type.'</code>' : $type;
        }
    }
    return $found;
} // End ddtt_get_php_eol()

The problem I am having is that it is recognizing rn as two separate types and outputting [ 'n', 'r' ]. I want to output [ 'rn' ] if it is just using that type, or [ 'rn', 'n' ] if using both types, etc. How do I modify my code to correctly fetch all types used?