count the number of occurrence of each element in an array (in php)

Question

I want the number of occurrences of each element in array. Note: I can't use inbuilt function like array_count_values()

here's what I have tried.

$a = ['a','b','a','c','a','d'];

$output = [];

for ($i = 0; $i <= count($a);$ i++) {
    $count = 1;
    for($j = $i + 1; $j < count($a); $j++) {
        if ($a[$i] == $a[$j]) {
            $count++;
            $output[$a[$i]] = $count;
        }
    }
}

print_r($output);

Does this answer your question? [PHP - count specific array values](https://stackoverflow.com/questions/11646054/php-count-specific-array-values) — stud3nt, Jan 21 '20 at 06:23
U need to use `array_count_values()` https://www.php.net/manual/en/function.array-count-values.php — CodyKL, Jan 21 '20 at 06:23
Okay, so what's wrong with your current solution? Explain desired inputs, outputs and actual results/errors. — Progrock, Jan 21 '20 at 06:25
You should tell your interviewer that reinventing the wheel is a waste of everyone's time... — Nick, Jan 21 '20 at 06:34

score 3 · Answer 1 · answered Jan 21 '20 at 06:30

In PHP7 you can use the NULL coalescing operator to simplify this code:

$a=['a','b','a','c','a','d'];

$output=[];

foreach ($a as $v) {
    $output[$v] = ($output[$v] ?? 0) + 1;
}

print_r($output);

Output:

Array
(
    [a] => 3
    [b] => 1
    [c] => 1
    [d] => 1
)

Demo on 3v4l.org

score 1 · Accepted Answer · answered Jan 21 '20 at 06:35

1

As mentioned in the comments array_count_values() is the optimal solution in php. But you must write it out aka show your understanding on how to search an array its rather simple as well.

$a=['a','b','a','c','a','d'];
$output=[]; 

for($i = 0; $i < count($a); $i++){
    if(!isset($output[$a[$i]])){
      $output[$a[$i]] = 1;
    }

    else{
        $output[$a[$i]] = $output[$a[$i]] + 1;
    }
}

var_dump($output);

//output
array(4) {
  ["a"] => int(3)
  ["b"] => int(1)
  ["c"] => int(1)
  ["d"] => int(1)
}

answered Jan 21 '20 at 06:35

jgetner

691
6
14

3

OP stipulates no use of inbuilt functions, and yet here we have `isset` and `count` and the OP has for now accepted this answer. – Progrock Jan 21 '20 at 07:07
I agree but this isn't about built in functions as both an isset and count can be accomplished with user built functions and loops. I think its more about the op's comfort with standardized things across many languages and versions. – jgetner Jan 21 '20 at 20:39
`isset` is quite trickly to replace with a user built function prior to the null coalescing operator. – Progrock Jan 21 '20 at 21:23
But yes it's vague as to whether the OP wants to totally omit in-built functions or just the function that would shortcut to the wanted result. – Progrock Jan 21 '20 at 21:30

score 1 · Answer 3 · answered Jan 21 '20 at 06:36

1

<?php
$items=['a','b','a','c','a','d'];

foreach($items as $item) {
    $result[$item] ??= 0;
    $result[$item]  += 1;
}

var_dump($result);

Output:

array(4) {
  ["a"]=>
  int(3)
  ["b"]=>
  int(1)
  ["c"]=>
  int(1)
  ["d"]=>
  int(1)
}

answered Jan 21 '20 at 06:36

Progrock

7,373
1
19
25

count the number of occurrence of each element in an array (in php)

3 Answers3