array_intersect_key : intersection of two or more arrays considering keys only

array_intersect_key(): Intersection of two or more arrays considering keys only

This function takes two or more arrays as input and then returns the associative array containing all the keys in input array ( $array1) that are present in all of the arguments.

$new_array = array_intersect_key ($array1, $array2,....);

$array1 : Required , the input array which will be checked.
$array2 : Required , the keys to be matched with $array1.

Here keys are only used for comparison. ( In array_intersect() only values are used for comparison )

Example with two arrays

$first=array('One' =>1,'Two'=>2,'Three'=>3,'Four'=>'Fourth');
$second=array('One'=>1,'Two'=>2,'Third'=>3);

$result1=array_intersect_key($first,$second);
while (list ($key, $val) = each ($result1)) {
echo "$key -> $val <br>";
}

Output is here.

One -> 1 
Two -> 2

Keys of the first index are retained. ( no re-indexing done here) . The third element is not included as the key is different in both arrays.

Example with three arrays

$first=array('One' =>1,'Two'=>2,'Three'=>3,'Four'=>'Fourth');
$second=array('One'=>1,'Two'=>2,'Third'=>3);
$third=array('One'=>1);
$result1=array_intersect_key($first,$second,$third);
while (list ($key, $val) = each ($result1)) {
echo "$key -> $val <br>";
}

Output is here.

One -> 1

Difference between arrays considering values
Array REFERENCE

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