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PHP array_intersect_key() Function

Complete PHP Array Reference

Definition and Usage

The array_intersect_key() function compares two or more arrays, and returns an array with the keys and values from the first array, only if the key is present in all of the other arrays.

Syntax

array_intersect_key(array1,array2,array3...)

Parameter	Description
array1	Required. The first array is the array that the others will be compared with
array2	Required. An array to be compared with the first array
array3	Optional. An array to be compared with the first array

Tips and Notes

Tip: You can compare the first array with one array, or as many as you like.

Note: Only the key is used in the comparison.

Example 1

<?php
$a1=array(0=>"Cat",1=>"Dog",2=>"Horse");
$a2=array(2=>"Bird",0=>"Cat",4=>"Fish");
print_r(array_intersect_key($a1,$a2));
?>

The output of the code above will be:

Array ( [0] => Cat [2] => Horse )

Example 2

<?php
$a1=array(0=>"Cat",1=>"Dog",2=>"Horse");
$a2=array(2=>"Bird",3=>"Rat",4=>"Fish");
$a3=array(2=>"Dog",6=>"Cow",7=>"Bird");
print_r(array_intersect_key($a1,$a2,$a3));
?>