This is what you would expect php to deliver if there was a built-in function named ucsentence.

function ucsentence ($string){
    $string = explode ('.', $string);
    $count = count ($string);
    for ($i = 0; $i < $count; $i++){
        $string[$i]  = ucfirst (trim ($string[$i]));
        if ($i > 0){
            $string[$i] = '&nbsp;&nbsp;' . $string[$i];
        }
    }
    $string = implode ('.', $string);
    return $string;
}