Código:
<script type="text/javascript">
function loadidcarrera()
{
var cbocarrera=document.getElementById("cbocarrera");
var id=cbocarrera.selectedIndex;
var req=new XMLHttpRequest();
//req.overrideMimeType('text/xml');
//req.setRequestHeader("Content-Type", "text/html");
req.open("GET","matricula.php?i="+id,true);
req.send("");
req.onreadystatechange = function(){
if(req.readyState==4){
if(req.status==200){
alert('ok');
}
}else{
alert("Cagado");
}
};
}
</script>
<body>
<?php
$cn=new mysqli("localhost","root","43781406","matricula");
$rs=$cn->query("SELECT id,especialidad FROM tb_especialidad");
$codcarrera=array();
$cont=0;
if(!isset($_GET['i']))
{
$_GET['i']=0;
}
?>
<form name="frmmatri" method="post" action="registrar.php">
<table border="1" align="center">
<thead>
<tr>
<th colspan="2">
Matricula
</th>
</tr>
</thead>
<tbody>
<tr>
<td>Numero</td>
<td><input type="text" name="txtnum" /><input type="hidden" name="frm" value="matricula"/></td>
</tr>
<tr>
<td>Alumno</td>
<td><input type="text" name="txtalu" /></td>
</tr>
<tr>
<td>Especialidad</td>
<td>
<select name="cboespecialidad" onchange="loadidcarrera()" id="cbocarrera">
<?php while($row=$rs->fetch_row()){?>
<option><?php echo $row[1]; $idcarrera[$cont]=$row[0]; $cont++?></option>
<?php }?>
</select>
<input type="hidden" value="<?php echo $idcarrera[$_GET['i']];?>" name="idespecialidad" />
</td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" name="btnreg" value="Registrar"/></td>
</tr>
</tbody>
</table>
</form>
<?php
echo $_GET['i'];
?>
</body>
</html>
