Warning: 0 is not a MySQL result index

$per = array ("printemps", "ete", "hiver"); 
$i=0;
	while($i<3)
  	{
     echo "<td  valign=top >";
     
    
    	$requet1=mysql_query("SELECT id_sejour,nom_sejour FROM sejour where periode_sejour='$per[$i]' ORDER BY `sejour.id_sejour`");	//sélection voyages printemps

	echo "<font color=\"red\" size=\"1\" face=\"Verdana\"  ><b>Séjours $per[$i]</b></font><br>";
	

	
echo $requet1;	
	
	while ($ligne1 = mysql_fetch_array($requet1))
		{
	

		echo "<img SRC=\"0.gif\"> <font color=\"navy\" size=\"2\" face=\"Verdana\" ><strong>"; 
      		echo "$ligne1[id_sejour]";        
		echo " - ";
		echo "$ligne1[nom_sejour]"; //affichage du nom_sejour de la table sejour
		echo "</strong></font><br>";
	
		$requet_peri=mysql_query("SELECT date_debut, date_fin, nom_sejour, id_voyage FROM voyage,sejour where voyage.sejour=sejour.nom_sejour and sejour.periode_sejour='$per[$i]' ");	
			while ($sej1 = mysql_fetch_array($requet_peri))
			{
				if ($sej1[nom_sejour]==$ligne1[nom_sejour])
				{
				echo "$v";
				echo "<a href=voyage.php3?id=".$id."&v=".$sej1[3].">$sej1[date_debut] $sej1[date_fin]</a>";  
				echo "<br>";
				}
			}
	echo "<br>";
		}
  	$i=$i+1;
  	echo "</td>";
  	}

while ($ligne1 = mysql_fetch_array($requet1))