Count dates inside an array PHP

Question

I have this Array :

Array (
[0] => Array ( [x] => 2016-04-19 ) 
[1] => Array ( [x] => 2016-05-25 ) 
[2] => Array ( [x] => 2016-05-26 ) 
[3] =&g         


        

Answer 1

Using array_map you can convert the dates to strings, then you can use array_count_values:

$theArray = array(array('x' => new DateTime('2016-04-19')), 
    array('x' => new DateTime('2016-04-19')),
    array('x' => new DateTime('2016-04-19')),
    array('x' => new DateTime('2016-05-19')));

function formatDate($d) {
    return $d['x']->format('Y-m-d');
}
$results = array_map("formatDate", $theArray);

print_r(array_count_values($results));

.

Array (
    [2016-04-19] => 3
    [2016-05-19] => 1 
)

Then you can use this to determine the duplicates.

(This would also be useful if the dates contained time elements that you wanted to ignore.)

Answer 2

Did you say count only duplicates? Well, you may just loop through the Array of given Dates and bundle the Duplicates into a new array and afterwards get the count of the resulting array like so:

    <?php


        $arrHolder      = array();
        $arrDuplicates  = array();
        $arrDateList    = array(
            "date1"     => '2016-04-19',
            "date2"     => '2016-05-25',
            "date3"     => '2016-05-26',
            "date4"     => '2016-05-27',
            "date5"     => '2016-05-28',
            "date6"     => '2016-05-29',   //<== DUPLICATE DATE : 1
            "date7"     => '2016-05-29',   //<== DUPLICATE DATE : 2
            "date8"     => '2016-06-02',
            "date9"     => '2016-06-03',
            "date10"    => '2016-06-07',
            "date11"    => '2016-06-10',
            "date12"    => '2016-06-17',
            "date13"    => '2016-06-24',
            "date14"    => '2016-05-29',   //<== DUPLICATE DATE : 3
            "date15"    => '2016-05-29',   //<== DUPLICATE DATE : 4
        );

    // LOOP THROUGH ALL THE GIVEN ARRAYS CHECKING IF ANY OF THEM ALREADY EXIST
    // IF NOT, WE JUST PUSH THE DATE TO $arrHolder ARRAY
    // OTHERWISE WE PERFORM MORE CHECK AND PUSH IT INTO A MULTI-DIMENSIONAL ARRAY: $arrDuplicates.  
    foreach($arrDateList as $key=>$date){
        if(!in_array($date, $arrHolder)){
            $arrHolder[$key]                    = $date;
        }else{
            if(!array_key_exists($date, $arrDuplicates)){
                // IF THIS KEY EXIST, IT MEANS THAT THIS IS THE 2ND INSTANCE
                // SO WE ASSIGN A COUNT OF 2 TO IT.
                $arrDuplicates[$date]           = array($key=>$date, "count"=>2);
            }else{
                $arrDuplicates[$date]["count"]  =  intval($arrDuplicates[$date]["count"])  + 1;
            }
        }
    }

    var_dump($arrDuplicates);

RESULT OF VAR_DUMP

        // YOU CAN SEE THE COUNT (NUMBER OF DUPLICATES)
        // AS WELL AS THE KEY AND EVEN THE DATE.... :-) 
        // NO NEED FOR EXTRA LOGIC THE $arrDuplicates HAS THEM ALL
        // YOU ONLY HAVE TO PEEK IN....         
        array (size=1)
          '2016-05-29' => 
            array (size=2)
              'date7' => string '2016-05-29' (length=10)
              'count' => int 4

Answer 3

Get the column you need and count the values:

$count = array_count_values(array_column($array, 'x'));

Then to find duplicates get the difference between the counts of 1 and the counts greater than 1:

$dupes = array_diff(array_flip($count), array_keys($count, 1));