<?php
$text = $_GET['text'];

$newText = "";
$word = "";

for ($i=0; $i < strlen($text); $i++) {
    if (ctype_alpha($text[$i])) {
        $word .= $text[$i];
    } else {
        if(ctype_upper($word)){
            if(strrev($word) == $word){
                for($j = 0; $j < strlen($word); $j++){
                    $newText .= $word[$j] . $word[$j];
                }
            } else {
                $newText .= strrev($word);
            }

        } else {
            $newText .= $word;
        }
        $newText .= $text[$i];
        $word = "";
    }
}

echo '<p>' . htmlspecialchars($newText) .'</p>';