Erreur

Bonsoir que ce que signifie cette erreur que ce que je dois modifier;;



Notice: Use of undefined constant i - assumed 'i' in C:\Users\CBS-COMPUTER\Desktop\EasyPHP-5.3.3.1\www\doc1\commande_cli_veh.php on line 243
voici le code
<?php

//connexion a la base
$connection = mysql_connect("localhost","root","");
if ( ! $connection )
die ("connection impossible");

//On sélectionne la BDD
$mabasededonnee="bdd";
mysql_select_db($mabasededonnee) or die ("pas de connection");

$e=$_SESSION['log_cli'];
$req=mysql_query("select * from commande_vehicule")or die( mysql_error() );



while ( $lign=mysql_fetch_row($req)){

$req1=mysql_query("select * from commande where (login_client='$e') AND (valid_cmd='0') AND (num_com='".$lign[2]."')") or die( mysql_error() );

//$req=mysql_query("select * from commande where ((login_client='$e') && (valid_cmd='0') && (num_com='".$lign[2]."'") or die( mysql_error() );}
$i=0;
while ($i<mysql_num_rows($req1))

{
$ligne=mysql_fetch_row($req1);


echo"
<table class='affich' align='center' cellspacing='1' >
<tr>
<td width=70%>
<b>Numéro commande :</b> ".$ligne[0]."
";$r=mysql_query("select * from client where login_client='$ligne[1]'") ;
$li=mysql_fetch_row($r);
echo"
<br><b>Nom client : </b>".$li[1]."
<br><b>Prénom client : </b>".$li[2]."<br>

<br><b>Quantité X Prix U</b> | <b>Nom Produit</b> <br><br>
";


$az=mysql_query("select * from commande_vehicule where num_commande='$ligne[0]'") ;
$k=0;
while ($k<mysql_num_rows($az)){

$zz=mysql_fetch_row($az);


$produit=mysql_query("select * from vehicule where num_vehi='$zz[1]'") ;


$pro=mysql_fetch_row($produit);
echo "(".$zz[3]." X ".$pro[19]." DA) -------- ".$pro[4]."<br>";

$k=$k+1; }
echo"

<br><b>Montant Total à payer : </b>".$ligne[2]." DA

</td>

<td align=center>
<div id='aj_panier'><a href=\"#\" onClick=\"confirme('".$ligne[0]."')\" >Annuler Commande</a>
</div>";
echo"</td></tr>
</table>";
echo"";
echo"<HR>";
$i=i+1;
}

}