Mine

0
Array
(
    [id_societe] => 28,
    [etc...]  
)
composant
Array
(
    [0] => Array
        (
            [id_societe_composant] => 25
            [id_societe] => 3131
            [id_composant] => 37
        )

    [1] => Array
        (
            [id_societe_composant] => 23
            [id_societe] => 3131
            [id_composant] => 28
        )
)

Print_r du tableau $societe_composant (le resultat a la sortie du test) :

Array
(
    [0] => Array
        (
            [id_societe] => 28,
            [etc...] 
        )

    [1] => Array
        (
            [0] => Array
                (
                    [id_societe_composant] => 25
                    [id_societe] => 3131
                    [id_composant] => 37
                )

            [1] => Array
                (
                    [id_societe_composant] => 23
                    [id_societe] => 3131
                    [id_composant] => 28
                )
        )

)