Count surplus entries of duplicate values in an array

Question

I need count of duplicate values in my array.

[ 
 ['KRA_category' => 'Business'],
 ['KRA_category' => 'Business'],
 ['KRA_category' => 'People'],
 ['KRA_category' => 'Business'],
 ['KRA_category' => 'Business'],
 ['KRA_category' => 'Business'],
];

Expected result:

['Business' => 4] 

• splash58: array_count_values() - php.net/manual/en/function.array-count-values.php
• LF-DevJourney: Possible duplicate of PHP - count specific array values
• Barmar: @KrisRoofe array_count_values can't be used for multi-dimensional arrays.
• LF-DevJourney: @Yeah, need some work before array_count_values
• Barmar: Why is it business = 4? There are 5 elements with KRA_category => Business.

Answer 1

You can combine array_column and array_count_values

$counts = array_count_values(array_column($array, 'KRA_category'));

For Business you would then use

$business_count = $counts['Business'] - 1;

to get the duplicates. -1 is to ignore the original and only count the extras.

• mickmackusa: This does not meet the brief: i need count of duplicate values in array for e.g. business=4.
• Barmar: @mickmackusa This gets the counts for every value. I've updated the answer to show how to get a the count for a specific value from that. I'm not sure how the OP is getting 4 instead of 5, I've asked them.
• mickmackusa: See how my answer ignores the first encountered value and only counts subsequently encountered values. I don't see any fogginess in the question.
• Barmar: Simply subtracting 1 from array_count_values seems simpler to me.
• mickmackusa: Then you have to filter out the zeros. This takes several cycles as I mention in my answer. My old answer (from years back) called array_walk() to decrement, but it felt too messy to me.

Answer 2

you can count the duplicate values in php with

$vals = array_count_values(array_column($array, 'KRA_category'));

supported in 5.5 and above.

• mickmackusa: This does not meet the brief: i need count of duplicate values in array for e.g. business=4.

Answer 3

To reduce the total cycles needed to isolate the elements that occur more than once, I'll demonstrate a foreach loop that will initialize a lookup array with a -1 value then increment it for every occurrence.

array_filter() is called to remove entries in the lookup which only got up to 0. This will leave only values that have a positive count after excluding the first occurrence.

Code: (Demo) (Alternative Syntax)

$array = [
 ['KRA_category'=>'Business'],
 ['KRA_category'=>'Business'],
 ['KRA_category'=>'People'],
 ['KRA_category'=>'Business'],
 ['KRA_category'=>'Business'],
 ['KRA_category'=>'Business']
];
foreach ($array as ['KRA_category' => $value]) {
 $result[$value] ??= -1;
 ++$result[$value];
}
var_export(array_filter($result));

Output:

array (
 'Business' => 4,
)

You can achieve the same result with a functional-style approach but this will require far greater computational time complexity. (Demo)

var_export(
 array_count_values(
 array_diff_key(
 array_column($array, 'KRA_category'),
 array_unique($array, SORT_REGULAR)
 )
 )
);