PHP

Bonjour, je débute en php et je ne sais pas ou est le probleme dans mon code ci dessous, il doit afficher un mot en pluriel mais il n'affiche rien:

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<?php
$con=@mysql_connect("localhost", "root", "");
mysql_select_db('sing_plu') or die("impossible d'ouvrir la base de donnees");

$mot_singulier=$_POST['Singulier'];
/*$len=strlen($mot_singulier);
$type=substr($mot_singulier,$len-2,2); */

$rep=mysql_query("select id_sing,type from singulier where mot='.$mot_singulier.'");

if (!$rep) {
echo 'Impossible d\'exécuter la requête : ' . mysql_error();
exit;
}
$donnees = mysql_fetch_array($rep);
echo $donnees['type'] ;
switch($donnees['type'])
{
case 'a':$rep1=mysql_query("select mot from type_ail where id_a=".$donnees['id_sing']."");
$var=mysql_fetch_array($rep1);
$pluriel=$var['mot_a'];
echo $pluriel ;
break;

case 'b':$rep1=mysql_query("select mot from type_al where id_b=".$donnees['id_sing']."");
$var=mysql_fetch_array($rep1);
$pluriel=$var['mot_b'];
echo $pluriel ;
break;

case 'c':$rep1=mysql_query("select mot from type_ou where id_c=".$donnees['id_sing']."");
$var=mysql_fetch_array($rep1);
$pluriel=$var['mot_c'];
echo $pluriel ;
break;

case 'd':$rep1=mysql_query("select mot from type_eau where id_d=".$donnees['id_sing']."");
$var=mysql_fetch_array($rep1);
$pluriel=$var['mot_d'];
echo $pluriel ;
break;
case 'e':$rep1=mysql_query("select mot from type_S where id_e=".$donnees['id_sing']."");
$var=mysql_fetch_array($rep1);
$pluriel=$var['mot_e'];
echo $pluriel ;
break;
}
mysql_close();
?>
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