Count duplicate values in an array

Question

I have a series of user data which each one is a list of comma separate values like italian, english. So first of all, I want to list each of them and that it is fine and works. But these values could be repeated and it is ok yet I would like to know the number of the repeated values in order to be able to says: American = 2. The code below shows me

Duplicates count: 5

But actually I should have only 2 duplicates as I can see from the admin panel

$stack = array();
$blogusers = get_users( 'orderby=nicename&role=author' );
foreach ( $blogusers as $user ) {
    $descTokens = explode(',', $user->user_description);
    $stack = array_merge($stack, $descTokens);
}
$count_values = array();
foreach ($stack as $a) {
    @$count_values[$a]++;
}
echo 'Duplicates count: '.count($count_values);

If I do print_r($count_values) i get

Array (
    [francese] => 1
    [ matematica] => 2
    [ inglese] => 1
    [fisica] => 1
    [ latino] => 1
)
Duplicates count: 5

And those aren't repeated strings.

@Qirel i have updated the question with the print_r result i get — rob.m
– rob.m, Commented Apr 10, 2017 at 23:57
So you have 1 duplicate value, which is present two times in your array? — Qirel
– Qirel, Commented Apr 11, 2017 at 0:01

Qirel · Accepted Answer · 2017-04-11 00:30:38Z

2

Using array_count_values() you would get the same output as your secondary foreach loop. A count() of this would, by your example, give you 5 - francese, matematica, inglese, fisica and latino would be entries with at least 1 as the value and counted as one each (by your example, the index 'matematica' would hold the value 2 instead of 1, as its a duplicate and appears twice, but will still be counted as one).

So if you then filter away all values which appears once, you should get what you're looking for. Use array_map() with a callback that removes all values that are one or less would be like this

foreach ($blogusers as $user) {
    $descTokens = explode(',', $user->user_description);
    $stack = array_merge($stack, $descTokens);
}
echo array_sum(array_map((function ($v) { return $v > 1 ? $v : 0; }), array_count_values($stack)));

Live demo

If you want an array with the values which only appears multiple times, you can replace array_sum() with array_filter() (that returns an array, so you can no longer echo it directly)

print_r(array_filter(array_map((function ($v) { return $v > 1 ? $v : 0; }), array_count_values($stack))));

Outputs

Array (  
    [twice] => 2  
)

See https://3v4l.org/WOObc for a working example on that.

edited Apr 11, 2017 at 0:30

answered Apr 11, 2017 at 0:19

Qirel

26.6k7 gold badges54 silver badges71 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Qirel Over a year ago

Using array_* functions often simplify working with arrays very much - then you don't have to loop as much, and there's almost always a function suitable for what you need ;-) This can of course be split into more lines, which could help readability of the code.

Manuel Otto · Accepted Answer · 2017-04-11 00:27:54Z

1

Add this at the end of your code to only have duplicates in $count_values

$total_duplicates = 0;
foreach ($count_values as $key=>$count) {
    if($count<=1){
        unset($count_values[$key]);
    }else{
        $total_duplicates += $count;
    }
}

This will remove any entries that are not duplicate (occuring once) via unset(). Also $total_duplicates will give you the total count of duplicates.

To output that as html do this:

echo '<p>You have '.$total_duplicates.' duplicates.</p>';
foreach ($count_values as $key=>$count) { 
    echo '<li>'.$key.' '.$count.'</li>'; 
}

edited Apr 11, 2017 at 0:27

answered Apr 11, 2017 at 0:15

Manuel Otto

6,5401 gold badge22 silver badges25 bronze badges

5 Comments

rob.m Over a year ago

ok great, this gives me the correct number. Now is it possible to place this result next to each list in order to find out how many of the same are in place? Like Italian 2

Manuel Otto Over a year ago

with list you mean $stack?

rob.m Over a year ago

oh sorry, i mean that then i output them as <li><?php echo $stack[0]; ?></li> <li><?php echo $stack[1]; ?></li> and ideally I would like to be able to have a count for each

rob.m Over a year ago

So $stack[0]; + Num etc will auto generate? Can you elaborate it more in your answer please? I think this is getting right where I what I was looking for

Manuel Otto Over a year ago

sure just iterate through $count_values again: foreach ($count_values as $key=>$count) { echo '<li>'.$key.' '.$count.'</li>'; }

flex_ · Accepted Answer · 2017-04-11 00:02:28Z

1

//Count of the duplicate array values 
$count = count(array_count_values($stack));
echo $count;

answered Apr 11, 2017 at 0:02

flex_

7333 gold badges11 silver badges29 bronze badges

5 Comments

rob.m Over a year ago

that gives me 5, it doesn't tell me "you have 2 of this and 3 of that"

zerkms Over a year ago

@rob.m you did not ask for "you have 2 of this and 3 of that" in your question. You only complained that the overall number of duplicates is wrong.

flex_ Over a year ago

i don't really know if that's possible. but then again i'm not good at arrays

rob.m Over a year ago

if i do this i'm almost there $count_values = array(); foreach ($stack as $a) { @$count_values[$a]++; } print_r(array_count_values($count_values));

rob.m Over a year ago

yet that results number Array ( [1] => 4 [2] => 1 should be placed correctly next to each list results )

Collectives™ on Stack Overflow

Count duplicate values in an array

3 Answers 3

1 Comment

5 Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

5 Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related