从数组中选择某些元素

Question

I'm trying to remove everything from an array except DTSTART & DTEND

So I'm trying to convert this:

Array
(
[0] => Array
    (
        [DTEND] => 20130417
        [DTSTART] => 20130403
        [UID] => [e-mail]
        [DESCRIPTION] => CHECKIN:  04/08/2012
CHECKOUT: 04/17/2012
NIGHTS:   14
PHO
        [NE] =>     [phone]
EMAIL:    [e-mail]
PROPERTY: Breathtaking views over the lake

        [SUMMARY] => Name here (ED5ASC)
        [LOCATION] => Breathtaking views over the lake
    )

[1] => Array
    (
        [DTEND] => 20131231
        [DTSTART] => 20131226
        [UID] => [e-mail]
        [DESCRIPTION] => CHECKIN:  12/26/2013
CHECKOUT: 12/31/2013
NIGHTS:   5
PHON
        [E] =>     [phone]
EMAIL:    [e-mail]
PROPERTY: Breathtaking views over the lake

        [SUMMARY] => Name here (JrtyKW9)
        [LOCATION] => Breathtaking views over the lake
    )

[2] => Array
    (
        [DTEND] => 20121123
        [DTSTART] => 20121117
        [UID] => [e-mail]
        [SUMMARY] => Not available
    )

)

to look like this:

Array
(
[0] => Array
    (
        [DTEND] => 20130417
        [DTSTART] => 20130403
    )

[1] => Array
    (
        [DTEND] => 20131231
        [DTSTART] => 20131226
    )
)

[2] => Array
    (
        [DTEND] => 20121123
        [DTSTART] => 20121117
    )
)

I've searched for loads of options but I need to be able to just select these two elements and discard the rest, I will be using it with different arrays that have different values so can't just specify the elements to remove as they will vary.

Answer 1

$newArray = array();
foreach ($array as $k => $v) {
  $newArray[$k]['DTEND'] = $v['DTEND'];
  $newArray[$k]['DTSTART'] = $v['DTSTART'];
}

edit: an alternative, since you mentioned trying to do it with one of the array iterator functions..

array_walk($array, function(&$v){
  $v = array('DTEND' => $v['DTEND'],'DTSTART' => $v['DTSTART']); 
});

edit2: because I have no life...yet another alternative...

array_walk($array, function(&$v){
  $v = array_intersect_key($v, array_flip(preg_grep('~^DT(END|START)$~', array_keys($v))));
});

I don't know which one is fastest/most efficient but my money is probably on the 2nd one.