Php count duplicate elements in an array and concat of ids

Question

How can we find the count of duplicate elements in a multidimensional array and concat of ids ?

I have an array of skill names with feed ids. I need to count skill name and concat of feed ids.

Array
(
    [0] => Array
        (
            [skill_name] => PHP
            [feed_id] => 100
        )
    [1] => Array
        (
            [skill_name] => CSS
            [feed_id] => 105
        )
    [2] => Array
        (
            [skill_name] => Php
            [feed_id] => 110
        )
    [3] => Array
        (
            [skill_name] => Php
            [feed_id] => 111
        )
    [4] => Array
        (
            [skill_name] => CSS
            [feed_id] => 112
        )
    [5] => Array
        (
            [skill_name] => Javascript
            [feed_id] =>114
        )
}

Output should be like below.

Array
(
    [0] => Array
        (
            [skill_name] => PHP
            [feed_id] => 100, 110, 111
            [count]=>3
        )
    [1] => Array
        (
            [skill_name] => CSS
            [feed_id] => 105, 112
            [count]=>2
        )
    [2] => Array
        (
            [skill_name] => Javascript
            [feed_id] => 114
            [count]=>1
        )

}

Thanks in advance!!

Eugen Rieck · Accepted Answer · 2015-02-22 11:30:10Z

1

//Assumption: Input is in $in

//Step 1: Cumulate
$tmp=array();
foreach ($in as $skill) {
  if (isset($tmp[$skill['skill_name']]))
    $tmp[$skill['skill_name']][]=$skill['feed_id'];
  else
    $tmp[$skill['skill_name']]=array($skill['feed_id']);
}

//Step 2: Fix up desired output format
$out=array();
foreach ($tmp as $k=>$v)
  $out[]=array(
    'skill_name' => $k,
    'feed_id' => implode(', ', $v),
    'count' => sizeof($v)
  );

//Result is in $out

answered Feb 22, 2015 at 11:30

Eugen Rieck

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2 Comments

orangetime Over a year ago

@ Eugen, skill_name should be case-insensitive. In your code Php and PHP returns duplicates.

Eugen Rieck Over a year ago

Well, add some strtoupper() to the first loop!

mickmackusa · Accepted Answer · 2019-08-22 11:38:29Z

This is perfectly achievable with a single loop using temporary keys and simple concatenation and incrementation.

Code: (Demo)

$array = [
    ['skill_name' => 'PHP', 'feed_id' => 100],
    ['skill_name' => 'CSS', 'feed_id' => 105],
    ['skill_name' => 'Php', 'feed_id' => 110],
    ['skill_name' => 'Php', 'feed_id' => 111],
    ['skill_name' => 'CSS', 'feed_id' => 112],
    ['skill_name' => 'Javascript', 'feed_id' => 114]
];

foreach ($array as $row) {
    $upperSkill = strtoupper($row['skill_name']);
    if (!isset($result[$upperSkill])) {
        $result[$upperSkill] = $row + ['count' => 1];  // plus acts as array_merge here
    } else {
        $result[$upperSkill]['feed_id'] .= ",{$row['feed_id']}"; // concatenate
        ++$result[$upperSkill]['count'];  // increment
    }
}
var_export(array_values($result));  // reindex and display

Output:

array (
  0 => 
  array (
    'skill_name' => 'PHP',
    'feed_id' => '100,110,111',
    'count' => 3,
  ),
  1 => 
  array (
    'skill_name' => 'CSS',
    'feed_id' => '105,112',
    'count' => 2,
  ),
  2 => 
  array (
    'skill_name' => 'Javascript',
    'feed_id' => 114,
    'count' => 1,
  ),
)

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