php extract sub array with specific key -

if have following array:

array(    'var1' => 123,    'var2' => 234,    'var3' => 345 );

i extract specific parts of build new array i.e. var1 , var3.

the result looking is:

array(    'var1' => 123,    'var3' => 345 );

the example posted stripped down, in reality array has larger number of keys , looking extract larger number of key , keys may or may not present.

is there built in php function this?

edit:

the keys extracted hardcoded array in class i..e $this->keystoextract

$result = array_intersect_key($yourarray,array_flip(array('var1','var3')));

so, edit:

$result = array_intersect_key($yourarray,array_flip($this->keystoextract));

EXIT