PHP array_replace without creating keys

Question

I am trying to overwrite the elements of one array with values from another – without creating additional elements in the process.

For example:

$base = array('a' => 'apple', 'b' => 'banana');
$replace = array('a' => 'orange', 'b' => 'grape', 'c' => 'cauliflower');

Merge the arrays to create:

array('a' => 'orange', 'b' => 'grape'); // 'c' not included

Using array_merge or array_replace would properly overwrite the elements, but the resulting array would include elements not found in the first array.

How can I combine two arrays to create an array containing only keys from the first array, and the corresponding values from a second array?

Is there an existing PHP array function that can do this?

Thanks for your help!

Answer 1

You can use array_intersect_key and array_merge to do it:

$result = array_merge($base, array_intersect_key($replace, $base));

array_intersect_key isolates those elements of $replace with keys that already exist in $base (ensuring that new elements will not appear in the result) and array_merge replaces the values in $base with these new values from $replace (while ensuring that keys appearing only in $base will retain their original values).

See it in action.

It is interesting to note that the same result can also be reached with the order of the calls reversed:

$result = array_intersect_key(array_merge($base, $replace), $base);

However this version does slightly more work, so I recommend the first one.

Answer 2

print_r(array_intersect_key($replace, $base));