$str = "Please join me in this prayer. ��❤️";
$newStr = preg_replace_callback("/&#.....;&#.....;/", function($matches){return convertToEmoji($matches);}, $str);
print_r($newStr);
function convertToEmoji($matches){
    $newStr = $matches[0];
    $newStr = str_replace("&#", '', $newStr);
    $newStr = str_replace(";", '##', $newStr);
    $myEmoji = explode("##", $newStr);
    $newStr = dechex($myEmoji[0]) . dechex($myEmoji[1]);
    $newStr = hex2bin($newStr);
    return iconv("UTF-16BE", "UTF-8", $newStr);
}