assigning to an associative array slice in php

Question

In perl, I could assign a list to multiple values in a hash, like so:

# define the hash...
my %hash = (
  foo => 1,
  bar => 2,
  baz => 3,
);

# change foo, bar, and baz to 4, 5, and 6 respectively
@hash{ 'foo', 'bar', 'baz' } = ( 4, 5, 6 );

Is there any way to do the same in php? In fact, is there even a way to get a slice of an assoc array at all?

Answer 1

There is no equivalent to the Perl syntax. But you can make an array of the keys of interest and use that to change only part of your array.

$koi=array('foo', 'bar', 'baz' );
foreach($koi as $k){
  $myarr[$k]++; //or whatever
}

or

array_walk($myarr, create_function('&$v,$k','$v=(in_array($k,$koi))? $v*2 : $v;')); //you'd have to define $koi inside the function

Answer 2

A simple one-liner (some of these methods require newer versions of PHP than were available at the time of asking):

$hash = array(
    'foo'=>1,
    'bar'=>2,
    'baz'=>3,
);

$hash = array_merge( $hash, array( 'foo' => 4, 'bar' => 4, 'baz' => 5 ) );

PHP Manual entry for array_merge.

If you're looking to GET a set of specific array keys, you can use this:

$subset = array_intersect_key( $hash, array_fill_keys( array( 'foo', 'baz' ), '' ) );

PHP Manual entries for array_intersect_key and array_fill_keys.

Answer 3

Define the hash:

$hash = array(
  'foo' => 1,
  'bar' => 2,
  'baz' => 3,
);

# change foo, bar, and baz to 4, 5, and 6 respectively
list($hash['foo'], $hash['bar'], $hash['baz']) = array( 4, 5, 6 );

# or change one by one
$hash['foo'] = 1;
$hash['bar'] = 2;
$hash['baz'] = 3;

See the list() function in manual:

http://php.net/manual/en/function.list.php

Answer 4

In short, no. However, you could use a function like this:

function assignSlice($ar,$keys,$args) {
  if (count($keys) !== count($args)) {
    // may want to handle more gracefully;
    // simply returns original if numbers of keys and values
    // don't match
    return $ar;
  }                                                 
  foreach ($keys as $index=>$key) {
    $ar[$key] = $args[$index];
  }
  return $ar;
}

$test = array(
    'foo'=>1,
    'bar'=>2,
    'baz'=>3,
    );

$newtest = assignSlice($test,array('foo','bar'),array(4,5));

Edit: adjusted code in response OP's comment on question.