如何用从另一个php页面收到的字符替换数组中的字符

I am having a problem on replacing the character in array by character receive from another page through Ajax.

href="show.php?q=1";

when user clicks this link it goes to:

show.php

<?php
    session_start();
    $q = $_GET['q'];
    $query = mysql_query("SELECT mname FROM BClassroom WHERE slno='".$q."'");
    while($row = mysql_fetch_array($query)){
        $n = $name = strtoupper($row['mname']);
    }

    $_SESSION['name'] = $name;
    for($i = 0; $i < strlen($name); $i++){
        switch($name[$i]){
            case 'A':
                    $name[$i] = "A";
                  //  echo 'A'." ";
                    break;
            case 'E':
                    $name[$i] = "E";
                  //  echo 'E'." ";
                    break;
            case 'I':
                    $name[$i] = "I";
                   // echo 'I'." ";
                    break;
            case 'O':
                    $name[$i] = "O";
                  //  echo 'O'." ";
                    break;
            case 'U':
                    $name[$i] = "U";
                   // echo 'U'." ";
                    break;
            case ' ':
                    $name[$i] = "/";
                   // echo "/"." ";
                    break;
            default:
                    $name[$i] = "_";
                   // echo "_"." ";
                    break;
        }

    }
    echo "<p id='datatbl'>$name</p>";
?>

<fieldset>
<legend>START THE GUESS</legend>
<div>
    <?php
        $consonant = "BCDFGHJKLMNPQRSTVWXYZ";
          $len = strlen($consonant);
            for($j=0;$j<$len;$j++){         ?>  
                <button name='CharCheck' id="sahil" onclick=checkBollyChar(this.value) value='<?php echo $consonant[$j] ?>'><?php echo $consonant[$j] ?></button>
        <?php   }   
    ?>
    <p><span id="datatbl"></span></p>
</div>
<button onclick="showResult(this.value)" value="<?php echo $n; ?>">Show Result</button>
</fieldset>

<script>
   function checkBollyChar(str){
            if(str==""){
               document.getElementById("datatbl").innerHTML="";
               return;
            }else{
                  if (window.XMLHttpRequest) {
            // code for IE7+, Firefox, Chrome, Opera, Safari
                         xmlhttp = new XMLHttpRequest();
                            } else {
            // code for IE6, IE5
                       xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
                              }
               xmlhttp.onreadystatechange = function(){
                    if(xmlhttp.readyState == 4 && xmlhttp.status ==200){
                        document.getElementById("datatbl").innerHTML= xmlhttp.responseText;
                    }
               }
               xmlhttp.open("GET","handler.php?q="+str,true);
               xmlhttp.send();
            }
      buttonHide();
   }
</script>
<script>
   function showResult(str){
            if(str==""){
               document.getElementById("datatbl").innerHTML="";
               return;
            }else{
                  if (window.XMLHttpRequest) {
            // code for IE7+, Firefox, Chrome, Opera, Safari
                         xmlhttp = new XMLHttpRequest();
                            } else {
            // code for IE6, IE5
                       xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
                              }
               xmlhttp.onreadystatechange = function(){
                    if(xmlhttp.readyState == 4 && xmlhttp.status ==200){
                        document.getElementById("datatbl").innerHTML= xmlhttp.responseText;
                    }
               }
               xmlhttp.open("GET","Result.php?q="+str,true);
               xmlhttp.send();
            }
   }   
</script>

when user clicks on button name="charCheck", it should replace the "_" with the character if it matches with actual character in the word.

for "JURASSIC", it shows "_ U _ A _ _ I _ _" only vowels, so when user clicks button "J" then "_" in first place should be replace by "J".

thanks.