get the least Frequent item from array of objects - php

Question

I'm trying to output [device_id] of the least frequent [device_ip_isp] from this array.
Also, If the array only has two SharedDevice Object available, and having different [device_ip_isp], it should output the 2nd SharedDevice Object's [device_id]
array (
0 =>
SharedDevice::__set_state(array(
'device_no' => 1,
'device_id' => '82',
'device_ip_isp' => 'Verizon Fios',
)),
1 =>
SharedDevice::__set_state(array(
'device_no' => 2,
'device_id' => '201',
'device_ip_isp' => 'Spectrum',
)),
2 =>
SharedDevice::__set_state(array(
'device_no' => 3,
'device_id' => '312',
'device_ip_isp' => 'Verizon Fios',
)),
3 =>
SharedDevice::__set_state(array(
'device_no' => 4,
'device_id' => '9715',
'device_ip_isp' => 'Verizon Fios',
)),
4 =>
SharedDevice::__set_state(array(
'device_no' => 5,
'device_id' => '11190',
'device_ip_isp' => 'Verizon Fios',
)),
)
The output should be 201 because "Spectrum" is the least frequent.
I tried the following and had issues:
I'm not sure how I can sort the object variables before comparing to find the least frequent.
/*
$user->getUser_devices() will output the array shown above.
*/
leastFrequent($user->getUser_devices(), 5);
function leastFrequent($arr, $n){
// find the min frequency
// using linear traversal
$min_count = $n + 1;
$res = -1;
$curr_count = 1;
for ($i = 1; $i < $n; $i++) {
if ($arr[$i]['device_ip_isp'] == $arr[$i - 1]['device_ip_isp']) {
$curr_count++;
} else {
if ($curr_count < $min_count) {
$min_count = $curr_count;
$res = $arr[$i - 1]['device_id'];
}
$curr_count = 1;
}
}
// If last element is
// least frequent
if ($curr_count < $min_count) {
$min_count = $curr_count;
$res = $arr[$n - 1]['device_id'];
}
return $arr[$n]$res['device_id'];
}

Answer 1

Ok, below is the explanation of the snippet inside out.
array_column to get all the device_ip_isp values in a single array.
array_count_values to get the frequency of each value.
array_reverse to reverse the count frequency array since you need the latest share device ID incase of count collision for a minimum count value.
min to get the lowest value among all the frequency counts.
array_search to get the key of the first frequency min element.
In the end, we reverse the input array to immediate return the device IP the moment we find the key from the above step matching the current device_ip_isp.
Snippet:
<?php
function getLeastFrequentElement($arr){
$freqs = array_reverse(array_count_values(array_column($arr, 'device_ip_isp')));
$deviceIPISP = array_search(min($freqs), $freqs);
foreach(array_reverse($arr) as $sharedDevice){
if($sharedDevice->device_ip_isp === $deviceIPISP){
return $sharedDevice->device_id;
}
}
throw new Exception("No shared object found!");
}
echo getLeastFrequentElement($arr);
Online Demo