PHP - If any array values match then remove all of them - php

Question

I'm kind of stuck here on what I think must have quite a simple solution.
Say I have an array:
$A = array(1, 1, 2, 4, 6, 7, 7, 7, 13);
How could I possibly remove all of the values that occur more than once?
So I'm left with an array that looks like this
$A = array(2, 4, 6, 13);
I've tried using array unique, but that just removes duplicates leaving you with a single value. I need to use the following logic: if there are any values that match - then remove all of the values that match.

Answer 1

You could always try something like this.
$A = array(1, 1, 2, 4, 6, 7, 7, 7, 13);
$A = array_count_values($A);
foreach($A as $key => $value) {
if($value > 1)
unset($A[$key]);
}
$A = array_keys($A);
print_r($A);
edit: fixed error
Array
(
[0] => 2
[1] => 4
[2] => 6
[3] => 13
)

Answer 2

You can use array_filter() with a custom callback to filter out the array values which repeat more than once:
function removeDuplicates($array) {
$values = array_count_values($array);
return array_filter($array, function($item) use ($values) {
return $values[$item] === 1;
});
}
Usage:
$A = array(1, 1, 2, 4, 6, 7, 7, 7, 13);
print_r( removeDuplicates($A) );
Output:
Array
(
[2] => 2
[3] => 4
[4] => 6
[8] => 13
)
Demo.

Answer 3

You can do this with abit of coding.
First see this SO post to get a list of all the duplicates using array_unique:
php return only duplicated entries from an array
Then you'll have to loop through the duplicates returned from the link above and do an array_search to return the index of the values and then array_splice to actually remove it.
I don't know of any code that will do this in one step for you.

Answer 4

Try this (with PHP >= 5.3):
$A = array_keys(array_filter(
array_count_values($A),
function ($count)
{
return $count == 1;
}
));
Explanation:
array_count_values returns an array using the values of array as keys and their frequency in array as values.
array_filter Iterates over each value in the array passing them to the callback function (in this case anonymous function) . If the frequency is 1, the current value from array is returned into the result array.
array_keys returns the keys from the array, in this case the values with frequency equal to 1.
So, the compressed "one-line" form is:
$A=array_keys(array_filter(array_count_values($A),function($c){return $c==1;}));