La select funziona perfettamente, devo inserire il valore codice selezionato nel campo input type
il codice sorgente della pagina:

Codice PHP:
<?php
 
include 'config.php';
 
connect(); //connessione al DB
 
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript" src="ora/jquery-1.7.1.min.js"></script>

        <link rel="stylesheet" media="all" type="text/css" href="ora/jquery-ui-1.8.16.custom.css" />
        <script type="text/javascript" src="ora/jquery-ui-1.8.16.custom.min.js"></script>
        <script type="text/javascript" src="ora/jquery-ui-timepicker-addon.js"></script>
        
        <script type="text/javascript">
            
            $(function(){
                
        
                $('.example-container > pre').each(function(i){
                    eval($(this).text());
                });
            });
            
        </script>


<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Prenota</title>
</head>

<body>
 <script type="text/javascript">
                  var xmlhttp;

                      function mostraInfo(str)
                      {
                       xmlhttp=GetXmlHttpObject();
                              if (xmlhttp==null)
                               {
                               alert ("Browser does not support HTTP Request");
                                  return;
                                }
                                var url="#";
                                 url=url+"?q="+str;
                                  xmlhttp.onreadystatechange=stateChanged;
                                  xmlhttp.open("GET",url,true);
                                  xmlhttp.send(null);
                                   }

                                     function stateChanged()
                                     {
                                     if (xmlhttp.readyState==4)
                                      {
                                      document.getElementById("info").innerHTML=xmlhttp.responseText;
                                       }
                                       }

                                       function GetXmlHttpObject()
                                        {
                                        if (window.XMLHttpRequest)
                                        {
                                        // code for IE7+, Firefox, Chrome, Opera, Safari
                                        return new XMLHttpRequest();
                                         }
                                         if (window.ActiveXObject)
                                         {
                                          // code for IE6, IE5
                                           return new ActiveXObject("Microsoft.XMLHTTP");
                                           }
                                           return null;
                                           }
          </script>  

<?php 

     
function disponibilita($str,$disp) {
         
$fl=false;
              if  (
$str[0]==1) {$disp[]='Lunedì';
             }if (
$str[1]==1)  {$disp[]='Martedì'
             }if (
$str[2]==1)  {$disp[]='Mercoledì'
             }if (
$str[3]==1)  {$disp[]='Giovedì'
             }if (
$str[4]==1)  {$disp[]='Venerdì';
             }if (
$str[5]==1)  {$disp[]='Sabato'
             }if (
$str[6]==1)  {$disp[]='Domenica'
             }
         
         
$scelta=$_POST['settimana'];
    
        
$lungh_arraycount($disp);
         for (
$contatore=0$contatore $lungh_array$contatore++) {
         if (
$disp[$contatore]==$scelta) {$fl=true;} 
        
// echo "$disp[$contatore]
";
}//for
        //echo "
SCELTA EFFETTUATA".$scelta."<br/n>";
        //echo "
FLAG".$fl."<br/n>"; 
        
        return 
$fl;
        return 
$str;
         }//function
 
                        if (!isset(
$_POST['invia'])) { 
                                                                            //se non è stato premuto il tasto invia dal form, allora esegui il form
                  ?>
                
                                                      <form method="
post" action="#" id=settimana>
                                                     
                                                    
<label><h1>Prenota Analisi</h1></label>                        
                                                   <
labelSeleziona Paziente: </label>
                                                  <
select name="tipopaz" onChange="mostraInfo(this.value)">
                                                 -->
                                      <?
php
                                           
//Seleziono quelli che sono i pazienti
                                            
$query "SELECT cf,cognome,nome FROM `paziente`";
                                            
$result mysql_query($query);
                                            while(
$riga mysql_fetch_array($result)){
                                            echo 
"<option value='$riga[id]'>$riga[cf] $riga[cognome] $riga[nome]</option>";
                                           }
                                          
                                          
?>
                              </select>
                                                                             
                                  
                                                                            <legend>Giorno: </legend>
                                                                            <select name="settimana" >
                                                                                <option value="Lunedì" selected="selected" >Luned&igrave </option>
                                                                                 <option value="Martedì">Marted&igrave </option>
                                                                                <option value="Mercoled&igrave">Mercoled&igrave </option>
                                                                                <option value="Gioved&igrave">Gioved&igrave </option>                          
                                                                                <option value="Venerd&igrave" >Venerd&igrave </option>
                                                                                <option value="Sabato">Sabato</option>
                                                                                <option value="Domenica">Domenica</option>                          
                                                                                 </select>
                                                                                    
                                                                                  
        <div class="example-container">
               

Inserire Ora</p>
              <div>
                   <input type="text" name="example3" id="example3" value="" />
              </div>
          <script>   $('#example3').timepicker({}); </script> 
</div>
             
                        
                                                   <label> Tipo Prestazione: </label>
                                                  <select name="tipoprest" onChange="mostraInfo(this.value)">
                                                
                                      <?php
                                           
//Seleziono quelli che sono i pazienti
                                            
$query "SELECT codice,descrizione FROM tipoprestazione WHERE av=0";
                                            
$result mysql_query($query);
                                            while(
$riga mysql_fetch_array($result)){
                                            echo 
"<option value='$riga[id]'>$riga[codice] $riga[descrizione] </option>";
                                  
                                           }
                                       echo 
'<input type="text" name="codice" value="'.$riga['codice'].'" />';
                                          
?>
                              
                              </select>
             
             
             
             
             <input type="submit" name="invia" id="inv" value="Invia" />
             </form>                                                                    
<?php }//isset 
                  
else { // se è stato premuto il tasto invia
                  
$cont=0;
$query "SELECT disponibilita,cognome FROM medico";
                    
$result mysql_query($query);
                    while(
$riga mysql_fetch_array($result)){
        
/*        echo "ID: $riga[id] <br/n>";
                    echo "Codice: $riga[codice] <br/n>";
                    echo "Codice Fiscale: $riga[cf] <br/n>"; */
                    
                    
                //    echo "Disponibilit&agrave: $riga[disponibilita] <br/n>";
                    
                    
$stringa=$riga['disponibilita'];
                    
$cognome=$riga['cognome'];
                    
$disp=false;
                    
$val=disponibilita($stringa,$disp);
                    echo 
"Disponibilit&agrave: $stringa <br/n>";
                    if (
$val) {echo "Il Medico ".$cognome." è disponibile ".$_POST['settimana']; $cont=1; exit; }
                    
//echo "VALORE MAIN: ".$val."<br/n";
                    
}//while
                    
if ($cont==0) {echo "NESSUN MEDICO &Egrave DISPONIBILE ".$_POST['settimana'];
                             
//provo con un assistente
                                 //abilita assistente
                            
echo "PROVO CON UN ASSISTENTE"
                            
                            
                            
                      
                      
$query "SELECT tipoPrestazione,assistente FROM abilitaassistente WHERE tipoPrestazione='(qui dovrei inserire il codice selezionato dalla select)'";
                      
$result mysql_query($query);
                    while(
$riga mysql_fetch_array($result)){
                             
$assist=$riga['assistente'];
                            echo 
$assist;
                             }
//while
                              // if ($result) {  echo $assist; }
                    
                    
}//IF
                            


}//else

?>



</body>
</html>