$sql = "SELECT * FROM membre,log,sexe 
				WHERE num_membre = num_log
				AND membre.num_sexe = sexe.num_sexe
				AND (log.pseudo = '".$_POST['pseudo']."'
				OR membre.ville = '".$_POST['ville']."'
				OR membre.region = '".$_POST['region']."'
				OR membre.departement = '".$_POST['departement']."'
				OR sexe.num_sexe = '".$_POST['sexe']."')";
		$result = mysql_query ($sql);
		
		while($result2 = mysql_fetch_object ($result))
			{
				echo("$result2->nom_membre");
			}

<form action='recherche2.php' method='post'>
		<table>
			<tr>
				<td>Par pseudo:</td>
				<td>
					<input type='text' name='pseudo' size='20'>
				</td>
			</tr>
			<tr>
				<td>Par ville:</td>
				<td>
					<input type='text' name='ville' size='20'>
				</td>
			</tr>
			<tr>
				<td>Par région:</td>
				<td>
					<select name='region' size='1' >
						<?php
							$sql = "SELECT * FROM region";
							$result = mysql_query ($sql);
							
									echo("<option selected value=0>...");
							while ($result2 = mysql_fetch_object ($result))
								{
									echo("<option value='$result2->num_region'>$result2->nom_region");
								}
						?>
					</select>
				</td>
			</tr>
			<tr>
				<td>Par département</td>
				<td>
					<select name='departement' size='1' >
						<?php
							$sql = "SELECT * FROM departement";
							$result3 = mysql_query ($sql);
									
									echo("<option selected value=0>...");
							while ($result4 = mysql_fetch_object ($result3))
								{
									echo("<option value='$result4->num_departement'>$result4->nom_departement");
								}
						?>
					</select>
				</td>
			</tr>
			<tr>
				<td>Par sexe:</td>
				<td><select name='sexe' size='1' >
						<option selected value='0'>...
						<option value='1'>Homme
						<option value='2'>Femme
					</select> 
				</td>
			</tr>
		</table><br><br>
				<input type='submit' name='ok' value='Rechercher'>
	</form>