使用Ajax发布值

Question

I'm trying to post the value of input name="sub2" to process my query in my input="sub3". I used Ajax but the input name="sub3" still empty. The value of sub2 is came from dropdown option text, if option text value is Supplies It get only the 3 first letters of supplies, so now the value of sub2 is "SUP". That value what I need to post to function my query in my sub3 textbox. Help please?

This is fiddle example http://jsfiddle.net/xqGLS/3/

Code.php

<?php
    $resultcode = $mysqli->query("SELECT category, id, maincode FROM category GROUP BY id ORDER BY maincode");
    $code = '';
     while($row = $resultcode->fetch_assoc())
        {
        $code .= '<option value = "'.$row['maincode'].'">'.$row['category'].'</option>';
        }   
?>
<form action="<?php $_SERVER['PHP_SELF']?>" method="POST">
<br/>

<label>Category</label>
<select name="maincode" style="text-transform:uppercase;" onchange = "GetChangedValue(this);">
<option value=""></option>
<?php echo $code; ?>
</select>

</br>

<label>Sub1</label>
<input type="" name="sub1" id="sub1" value="" readonly style="width:45px;text-transform:uppercase;">

<script>
$('[name="maincode"]').change(function() {
   $('[name="sub1"]').val($(this).val());
   var input = $('[name="sub2"],[name="sub3"]'),
    input1 = $('[name="sub2"]'),
    input2 = $('[name="sub3"]'),
    input3 = $('[name="equal"]');
    input.change(function () {
    input3.val(input1.val() + input2.val());
});
});
</script>

<script>
function GetChangedValue(e) {
var value = e.options[e.selectedIndex].text;
var elem = document.getElementById("sub2"); elem.value = value.substring(0,3);
}
</script>

<label>Sub2</label>
<input name="sub2" id="sub2" value="" style="width:35px;text-transform:uppercase;" readonly>

<label>Sub3</label>
<input id="sub3" name="sub3" style="width:35px;text-transform:uppercase;" value=''>

<script type="text/javascript">
$('#sub2').change(function(){
$.ajax({
url : 'check.php',
data :{mainlist_id : $(this).val()},
dataType:'html',
type:'POST',
success:function(data){
$('#sub3').html(data);
}
});
});
</script>

<input id="equal" name="equal" value="" style="width:60px;text-transform:uppercase;" type="hidden">
<input type="submit" name="">
</form>

Check.php

<?php
    $mysqli = new mysqli("localhost", "root", "", "2015");
    $sub = $mysqli->real_escape_string($_POST["mainlist_id"]);

$result2 = $mysqli->query("SELECT * FROM code
WHERE sub1code LIKE '$sub-___' ORDER BY sub1code");

while($row = $result2->fetch_assoc())
  {
  $value = $row['sub1code'];
  }
  $first = substr($value, 0, 4);
  echo $first;
  $last = substr($value, -3);
  $i="0";
  while($i<=$last)
  {
  $i++;
  }
  $value2=strlen($i);
    echo $first;
    if($value2==1)
    {
    echo "00".$i;
    }
    elseif($value2==2)
    {
    echo "0".$i;
    }
    else
    {
    echo $i;
    }
    ?>

Answer 1

I think you want something like this. Just a little change on your code but it should work.

Code.php

<script type="text/javascript">
function GetChangedValue(str) {
    if (str==""){
        document.getElementById("sub3").innerHTML="";
        return;
    }
    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("sub3").value = xmlhttp.responseText;
        }
    }
    xmlhttp.open("GET","check.php?q="+str,true);
    xmlhttp.send();
}
</script>

<select name="category" id="category" onchange="GetChangedValue(this.value);">
<option value=""></option>
<?php
$mysqli = new mysqli("localhost", "root", "", "2015");
$result2 = $mysqli->query("SELECT * FROM category ORDER BY maincode");
while($row = $result2->fetch_assoc())
{
$ok = $row['maincode'];
echo "<option value=".$row['maincode'].">".$row['category']."</option>";
}                               
?>
</select>


<input type="" name="sub3" id="sub3" value="" readonly style="width:85px;text-transform:uppercase;">

Check.php

<?php
if (isset($_GET["q"])) {
$q=$_GET["q"];
$mysqli = new mysqli("localhost", "root", "", "2015");

$sub = substr($q, 0, 4);

$result2 = $mysqli->query("SELECT * FROM code
WHERE sub1code LIKE '$sub-___' ORDER BY sub1code");

while($row = $result2->fetch_assoc())
  {
  $value = $row['sub1code'];
  }
  //$first = substr($value, 0, 3);
  echo $sub;
  $last = substr($value, -3);
  $i="0";
  while($i<=$last)
  {
  $i++;
  }
$value2=strlen($i);
if($value2==1)
{
echo "-"."00".$i;
}
elseif($value2==2)
{
echo "-"."0".$i;
}
else
{
echo "-".$i;
}
}
?>