Ottimizzazione array multidimensionale

[snaturone]

Ciao a tutti/e,

ho questo array come risultato di una query:

$PersoneSkills[] = array('idPersona' => $post_obj['idPersone'], 'idSkill' => $post_obj['idSkill']);
Array
(
    [0] => Array
        (
            [idPersona] => 133
            [idSkill] => 48
        )

    [1] => Array
        (
            [idPersona] => 191
            [idSkill] => 48
        )

    [2] => Array
        (
            [idPersona] => 133
            [idSkill] => 49
        )

    [3] => Array
        (
            [idPersona] => 191
            [idSkill] => 49
        )

    [4] => Array
        (
            [idPersona] => 133
            [idSkill] => 50
        )

    [5] => Array
        (
            [idPersona] => 133
            [idSkill] => 51
        )

    [6] => Array
        (
            [idPersona] => 191
            [idSkill] => 51
        )

    [7] => Array
        (
            [idPersona] => 133
            [idSkill] => 52
        )

    [8] => Array
        (
            [idPersona] => 133
            [idSkill] => 53
        )

    [9] => Array
        (
            [idPersona] => 191
            [idSkill] => 53
        )

    [10] => Array
        (
            [idPersona] => 133
            [idSkill] => 54
        )

    [11] => Array
        (
            [idPersona] => 133
            [idSkill] => 55
        )

    [12] => Array
        (
            [idPersona] => 133
            [idSkill] => 56
        )

    [13] => Array
        (
            [idPersona] => 191
            [idSkill] => 56
        )

    [14] => Array
        (
            [idPersona] => 133
            [idSkill] => 57
        )

    [15] => Array
        (
            [idPersona] => 191
            [idSkill] => 57
        )

    [16] => Array
        (
            [idPersona] => 133
            [idSkill] => 58
        )

    [17] => Array
        (
            [idPersona] => 191
            [idSkill] => 58
        )

    [18] => Array
        (
            [idPersona] => 133
            [idSkill] => 59
        )

    [19] => Array
        (
            [idPersona] => 191
            [idSkill] => 59
        )

) 

e vorrei ottimizzare il mio risultato con un risultato del tipo:

Array
(
    [133] => Array
        (
            [idSkill] => 48
            [idSkill] => 49
            [idSkill] => 50 // etc....
        )
    [191] => Array
        (
            [idSkill] => 48
            [idSkill] => 49
            [idSkill] => 50 // etc....
        )
) 

Come posso fare? Grazie.