combox anidados
conecto en php y cuando seleciono el primero el segundo no me lee alguien me ayude por favor:
<?php
echo "<select name='medico'>";
echo "<OPTION> selecione </OPTION>";
$llave = mysql_connect ("localhost", "root","");
mysql_select_db("ayudasalud", $llave);
$sql = mysql_query ("select * from medico", $llave);
while ($do = mysql_fetch_array($sql)){
$med= $do[nom_medic];
$rut = $do[rut_med];
echo "<option value='$rut'> $med </option>";
}
echo "</select>n";
echo "<select name='centro'>";
echo "<OPTION> selecione </OPTION>";
$result2 = mysql_query("SELECT * FROM atiende where rut_med = " . $_REQUEST['medico'] . " " , $llave);
$doo = mysql_fetch_array($result2);
$centro= $doo[id_centro];
echo "<option value='$centro'> $centro </option>";
echo "</select>n";
?>
<?php
echo "<select name='medico'>";
echo "<OPTION> selecione </OPTION>";
$llave = mysql_connect ("localhost", "root","");
mysql_select_db("ayudasalud", $llave);
$sql = mysql_query ("select * from medico", $llave);
while ($do = mysql_fetch_array($sql)){
$med= $do[nom_medic];
$rut = $do[rut_med];
echo "<option value='$rut'> $med </option>";
}
echo "</select>n";
echo "<select name='centro'>";
echo "<OPTION> selecione </OPTION>";
$result2 = mysql_query("SELECT * FROM atiende where rut_med = " . $_REQUEST['medico'] . " " , $llave);
$doo = mysql_fetch_array($result2);
$centro= $doo[id_centro];
echo "<option value='$centro'> $centro </option>";
echo "</select>n";
?>