<input name="a" value="a">
<input name="a" value="b">
<input name="a" value="c">
<input name="b">
<script>
window.onload = function()
{
v = "";
o = document.getElementsByName("a");
for(c=0;c<o.length;c++) v+=o[c].value;
document.getElementsByName("b")[0].value=v;
}
</script>
<input name="a" value="b">
<input name="a" value="c">
<input name="b">
<script>
window.onload = function()
{
v = "";
o = document.getElementsByName("a");
for(c=0;c<o.length;c++) v+=o[c].value;
document.getElementsByName("b")[0].value=v;
}
</script>
<input name="a" value="2">
<input name="a" value="3">
<input name="b">
<script>
window.onload = function()
{
v = 0;
o = document.getElementsByName("a");
for(c=0;c<o.length;c++) v+=parseInt(o[c].value);
document.getElementsByName("b")[0].value=v;
}
</script>
$num = 0;
for($i=0; $i<10; $i++){
$num +=$i;
?>
<input type="text" name="t1" value="<?php echo $i ?>"><br/>
<?php
}
?>
<br/><input type="text" name="t2" value="<?php echo $num?>">
</form>