Definition and usage
array_diff_key() function is used to compare the key names of two (or more) arrays and return the difference.
This function compares the key names of two (or more) arrays and returns a difference array that includes everything in the compared array (array1) but not in any other parameter array (array2 or array3, etc.).
Syntax
array_diff_key(array1,array2,array3...);
Parameter description:
array1 Required. The first array to compare with other arrays.
array2 Required. The array to compare to the first array.
array3,... Optional. Additional array to compare with the first array.
Return value:
Returns a difference array that includes all elements in the compared array (array1) that are not in any other parameter array (array2) or array3, etc.).
Example display 1:
<!DOCTYPE html>
<html>
<body>
<?php
$a1=array("a"=>"red","b"=>"green","c"=>"blue");
$a2=array("a"=>"red","c"=>"blue","d"=>"pink");
$result=array_diff_key($a1,$a2);
print_r($result);
?>
</body>
</html>Run result:
Array ( [b] => green )
Example display 2:
<!DOCTYPE html>
<html>
<body>
<?php
$a1=array("a"=>"red","b"=>"green","c"=>"blue");
$a2=array("c"=>"yellow","d"=>"black","e"=>"brown");
$a3=array("f"=>"green","c"=>"purple","g"=>"red");
$result=array_diff_key($a1,$a2,$a3);
print_r($result);
?>
</body>
</html>Run result
Array ( [a] => red [b] => green )
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