mistero di msql_query

<form name="form1" method="post" action="scrivi.php">
<p>Regione:<br> 
<select onChange="GetProvince(this.options[this.selectedIndex].text)" id="regione" name="regione">
      <option value="0"></option>
	  <?php 
		$cerca_R="select * from regioni order by id_R";
		$query_R= mysql_query($cerca_R);
		while ($riga_R= mysql_fetch_array($query_R)){
			$REG=$riga_R[regione];
			echo "<option value=\"".$REG."\>".$REG."</option>";
		}
		mysql_close();
	  ?>
    </select>
    <br>
    Provincia:<br> 
    <select id="provincia" name="provincia">
    </select>
    <br>
......

$query_R= mysql_query($cerca_R);
while ($riga_R= mysql_fetch_array($query_R)){ // primo while regioni
   $IDR=$riga_R[id_R]; //id primaria regioni
   $REG=$riga_R[regione];
   echo $REG." ".$IDR."<br>";
   $cerca_P= "select * from province where id_R='".$IDR."' order by id_P";
   $query_P=mysql_query($cerca_P);
   while ($riga_P= mysql_fetch_array($query_P)){ // secondo while province
		$IDP=$riga_P[id_P];// id primaria province
		$PRO=$riga_P[provincia];
		echo "&nbsp;&nbsp;".$PRO."&nbsp;&nbsp;".$IDP."<br>";
		//$elenco .= "\"".$PRO."\",";
		$elenco .= $PRO.",";
    }// fine secondo while
	//echo "elenco ".$elenco."<br>";
      $elenco = substr($elenco, 0,-1); // tolgo l’ultima virgola
	  //echo $elenco."<br>";
	  
      $province[$REG]=array($elenco);
	  $elenco="";
	  
   /*}// fine secondo while */
}// fine primo while

echo "<option value=\"".$REG."\">".$REG."</option>";