Problème avec les boucles

<?php 

date_default_timezone_set('Africa/Algiers') ;

set_time_limit(0);

$debut= date('H:i:s');

include ('connection.php');
$db=mysql_select_db("test");

$sql_cpt= "[/contents/1068-sql-commande-select SELECT] COUNT(id) as k FROM mdl_ens1";
$res_sql_cpt=mysql_query($sql_cpt);
if($res_sql_cpt==FALSE)
{die(mysql_error());
mysql_close();}
$rep_sql_cpt= mysql_fetch_array($res_sql_cpt);
{
mysql_free_result($res_sql_cpt);
$k=$rep_sql_cpt['k'];
echo ' nbr= '.$k.'<br>';

}
// connexion à la BDD

// REQUETE
$sql_sel= "SELECT heur_min_sec,date,mois,jour,heure,minute  FROM mdl_ens1";
$res_sql_sel=mysql_query($sql_sel) or die(mysql_error());

// Creation du tableau
$tab=array();
while ($line_sql_sel= mysql_fetch_array($res_sql_sel)) {
   $tab[]=$line_sql_sel["heur_min_sec"];
   $date[]=$line_sql_sel["date"];
   $mois[]= $line_sql_sel["mois"];
   $jour[]= $line_sql_sel["jour"];
   $heure[]= $line_sql_sel["heure"];
   $minute[]= $line_sql_sel["minute"];

}
mysql_close();   
   
    $i=-1;
    $j=0;
   while ($i++<$k-1)   
   {
   echo $i .'<br>';
   
if (($mois[$i]!=$mois[$i+1]) OR ($jour[$i]!=$jour[$i+1]))
{
break;
}

{$sous[$i]=(($heure[$i+1]*60)+($minute[$i+1]))-(($heure[$i]*60)+($minute[$i]));
echo $sous[$i].'<br>';
$som[$j]=$som[$j]+$sous[$i];
echo $som[$j].'<br>';
}
}
?>