Html存在字符前的制表符

I am printing some names in PHP. However is always exist a tab character at the begin and end of string . How can I remove the tab character. Here is my code, it still cannot remove the extra tab.

<strong>
    <?php 
       for ($i=0;$i <count($countrys);$i++){
             $country = preg_replace('/[\s]+/mu', ' ', $countrys[$i]);
             $country = trim($country);
             echo $country;
                  if ($i != count($countrys)-1){
                    echo ', ';
                  }
          }
    ?>
</strong>                

The outcome of the printing is like this.

    "  China, England, USA   "  

Be careful the space between html Tag and php code, browser will read the space between html tag and php echo

So just render it in one row

<strong><?php $countrys = ['a','v']; for ($i=0;$i<count($countrys);$i++){ $country = $countrys[$i]; echo $country; if ($i != count($countrys)-1){ echo ', '; } } ?></strong>

You can simply to check your raw html source after rendering to prevent unexpected space or row