如何在多维数组中计算相同的值？

Here I have an array. This is it:

Array ( Array (
     'name' => 'bmw',
     'id' => 1
 ), Array (
     'name' => 'toyota',
     'id' => 1
 ),Array ( 
     'name' => 'tata',
     'id' => 2 
 ),Array ( 
     'name' => 'bajaj',
     'id' => 3
 ),Array (
     'name' => 'kawasaki',
     'id' => 3
 ), Array (
     'name' => 'tvs',
     'id' => 3
 ),Array (
     'name' => 'mitsubishi',
     'id' => 2
 )
);

and what code should be next to give me result as id 1 => 2 items , id 2 => 2 items and id 3 => 3 items? I tried array_count_values() and it doesn't work for me.

According to documentation array_count_values works only on strings and integers. You can use it but first you should extract a column with ids. As of PHP 5.5 it's really easy, just call a function called array_column.

$list = array ( Array (
     'name' => 'bmw',
     'id' => 1
 ), Array (
     'name' => 'toyota',
     'id' => 1
 ),Array ( 
     'name' => 'tata',
     'id' => 2 
 ),Array ( 
     'name' => 'bajaj',
     'id' => 3
 ),Array (
     'name' => 'kawasaki',
     'id' => 3
 ), Array (
     'name' => 'tvs',
     'id' => 3
 ),Array (
     'name' => 'mitsubishi',
     'id' => 2
 )
);

$results = array_count_values(array_column($list, 'id'));

Maybe there is a nicer solution, but this should work.

Assuming that your array is saved in $arr.

$countItemsById = [];

foreach( $arr as $data ){
  $countItemsById[ $data['id'] ]++;
}

This code does the following: First it is creating a new Array $countItemsById. After that it loops trough your existing array and increases the value in the new array by 1 for the index (key) that has the value of the id.

After that, $countItemsById will look like this:

Array (1 => 2, 2 => 2, 3 => 3)

loop your array, to calculate the occerence for each id.

<?php
$list = array ( Array (
     'name' => 'bmw',
     'id' => 1
 ), Array (
     'name' => 'toyota',
     'id' => 1
 ),Array (
     'name' => 'tata',
     'id' => 2
 ),Array (
     'name' => 'bajaj',
     'id' => 3
 ),Array (
     'name' => 'kawasaki',
     'id' => 3
 ), Array (
     'name' => 'tvs',
     'id' => 3
 ),Array (
     'name' => 'mitsubishi',
     'id' => 2
 )
);

$results = [];
array_walk($list, function($v) use(&$results){
  $results[$v['id']]++;
});
var_dump($results);

output:

array(3) {
  [1]=>
  int(2)
  [2]=>
  int(2)
  [3]=>
  int(3)
}