18

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!

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5 Answers 5

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23

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.

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4 Comments

why not just array_intersect_key($replace, $base) ? while checking the documentation [link] php.net/manual/en/function.array-intersect-key.php "Also notice that the values for the keys 'blue' and 'green' differ between the two arrays. A match still occurs because only the keys are checked. The values returned are those of array1." So i dont think array_merge is required..
@coderkane: Because if $replace does not contain all the keys that $base has the result will have missing values.
I am aware, but the OP did say he wants values only from the second array. However, it is possible that he didn't foresee that scenario, so good point out.
@coderkane: "Overwrite elements of one array with values from another" -- IMHO this says the elements not in the other array should retain their existing values.
2 
print_r(array_intersect_key($replace, $base));
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3 Comments

Thanks everyone! I knew there had to be a simple solution.
@Jason: Please be aware that if $replace does not have values for all the keys in $base then the "missing" keys will not appear in the result at all.
Note that in this version, the resulting array will have keys in the order they appear in $replace, not $base - in case it matters
0

I can't think of a built in method for that, however, it would be trivial with a loop and array_key_exists.

foreach( $replace as $k => $v )
{
   if ( array_key_exists( $k, $base ) )
      $base[ $k ] = $v;
}
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0

the following should do it:

foreach ($replace as $k => $v)
   if (isset($base[$k])) $base[$k]=$v;
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0

Try this:

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