<?php



$db = new mysqli(...) ;

$sql =

	'select c.nom as nom

		, c.prenom as prenom

		, s.nom as societe 

	from contacts as c

		join societes as s

		on c.societe_id = s.id

	order by societe, nom, prenom

	' ;

$contacts = array() ;



$res = $db->query($sql) ;

if($res instanceof mysqli_result)

{

	while($row = $res->fetch_assoc())

		$contacts[] = $row ;

}

else

{

	/* erreur à traiter */

}



$societe = null ;



echo "<table>\n" ;

foreach($contacts as $idx => $contact)

{

	if($societe !== $contact['societe'])

	{

		echo "<tr>\n" ;

		$societe = $contact['societe'] ;

		echo "\t\t<td colspan='3'>".htmlentities($societe)."</td>" ;

		echo "\t</tr>\n" ;

	}

	else

	{

		echo "<tr>\n" ;

		$nom = $contact['nom'] ;

		$prenom = $contact['prenom'] ;

		$tel = $contact['tel'] ;



		echo "\t\t<td >".htmlentities($societe)."</td>\n" ;

		echo "\t\t<td >".htmlentities($nom)."</td>\n" ;

		echo "\t\t<td >".htmlentities($prenom)."</td>\n" ;



		echo "\t</tr>\n" ;

	}

}



echo "</table>\n" ;

SELECT societe_id, societe_nom, 

GROUP_CONCAT(contact_nom, ' ', contact_prenom, ', ' ORDER BY contact_nom SEPARATOR '\n') AS contact 

FROM contact

INNER JOIN societe ON contact_societe = societe_nom

GROUP BY societe_id, societe_nom;