PHP多维数组合

I am hoping to find help how to get to such structure:

[pad] => Array
    (
        [padi] => Array
            (
                [Date] => 2016-01-01
                [Val] => 1
                [Premium] => 100
            )
        [padi] => Array
            (
                [Date] => 2016-04-01
                [Val] => 1
                [Premium] => 200
            )
        [padi] => Array
            (
                [Date] => 2016-07-01
                [Val] => 1
                [Premium] => 300
            )
        [padi] => Array
            (
                [Date] => 2016-11-01
                [Val] => 1
                [Premium] => 400
            )

    )

I have 4 variables:

$p1 = array('padi' =>
                    array('Date' => $Date_0, 'Val' => $Val, 'padiPremium' => $padiPremium_0));
$p2 = array('padi' =>
                    array('Date' => $Date_1, 'Val' => $Val, 'padiPremium' => $padiPremium_1));
$p3 = array('padi' =>
                    array('Date' => $Date_1, 'Val' => $Val, 'padiPremium' => $padiPremium_1));
$p4 = array('padi' =>
                    array('Date' => $Date_1, 'Val' => $Val, 'padiPremium' => $padiPremium_1));

I have already tried with array_push, array_merge and array_combine and that didn't work for me at all or just my approach was wrong. I would be gratefull to any suggestions !

Unless I misunderstood you, you are trying to merge 4 arrays:

$merged = array();
$merged[]=$p1;
$merged[]=$p2;
$merged[]=$p3;
$merged[]=$p4;

var_dump($merged);

You cannot have multiple of the same key in an associative array (in you case: padi).