$sql2 ="select * from tables_psi.nb_fait_operation_periode where code_tranche = $1 ";

$marequete2 = pg_query_params(pg_connect("host=$serveur port=$port dbname=$base user=$_SESSION[identifiant] password=$_SESSION[mot_de_passe]"
), $sql2, array($_POST[code_tranche])) ;

?>

?php
...

echo "<div name='tableau2' >
        <table name='tableau_nbfaitop2' class='doc' >
            <thead>
                <tr>
                    <th>code_tranche</th>
                    <th>nom_operation</th>
                    <th>interpretation</th>
                    <th>période</th>
                    <th>date début</th>
                    <th>date fin</th>
                    <th>nombre</th>
                </tr>
            </thead>" ;
        while ($ligne2 = pg_fetch_array($marequete2)){
                echo "
            <tbody>
                <tr>
                    <td>$ligne2[code_tranche]</td>
                    <td>$ligne2[nomope]</td>
                    <td>$ligne2[interpret]</td>
                    <td>$ligne2[periode]</td>
                    <td>$ligne2[datedebut]</td>
                    <td>$ligne2[datefin]</td>
                    <td>$ligne2[nombre]</td>
                </tr>
            </tbody>" ;
        }
        "</table>
    </div>" ;
?>