Get only the array elements with certain keys [duplicate]

Answer 1

You can use FilterIterator

$iterator = new SpecialFilter($items, 'special');
var_dump(iterator_to_array($iterator));

Output

array
  'special_1' => string '3' (length=1)
  'special_2' => string '5' (length=1)
  'special_3' => string '6' (length=1)

Class Used

class SpecialFilter extends FilterIterator {
    private $f;
    public function __construct(array $items, $filter) {
        $object = new ArrayObject( $items );
        $this->f = $filter;
        parent::__construct( $object->getIterator() );
    }
    public function accept() {
        return 0 === strpos( $this->getInnerIterator()->key(), $this->f );
    }
}

Answer 2

First you need to get an array containing the keys. array_keys

Then, you need to filter the keys to find the ones you want. array_filter

Use this callback:

function($a) {return substr($a,0,8) == "special_";}

Then flip the array so that the keys are keys again instead of values. array_flip

Finally, intersect those keys with the original array. array_intersect_key

Result:

$special_items = array_intersect_key($items,array_flip(array_filter(array_keys($items),function($a) {return substr($a,0,8) == "special_";})));

Answer 3

How about this?

$special_items = array();

foreach($items as $key => $val) {
    if(substr($key, 0, 8) == 'special_')
        $special_items[$key] = $val;
}

Answer 4

how about

$keys = preg_grep( "/special_/i", array_keys( $items ) );

$new_array = array();

foreach( $keys as $k )
{
    $new_array[ $k ] = $items[ $k ];
}

Answer 5

$special_items = array_intersect_key(array_flip(preg_grep('/^special_\d+/', array_keys($items))), $items);

Please don't actually use that. Just use a foreach loop with strpos + an if statement like all normal people would.