add this function in the bottom file
function isNumberKey(evt) {
var charCode = (evt.which) ? evt.which : event.keyCode
if (charCode > 31 && (charCode < 48 || charCode > 57)) {
return false;
} else {
return true;
}
}
<input type="text" name="telephone" onkeypress="return isNumberKey(event)" value="<?php echo $telephone; ?>" size="32"/>
Thanks to : avvici -arvixe-