PHP sorty array by column and slice it - php

Question

I am trying to sort an array based on a column value:
Example:
$cats[0]['holders'] = 55;
$cats[1]['holders'] = 66;
$cats[2]['holders'] = 77;
$cats[3]['holders'] = 23;
$cats[4]['holders'] = 64;
$cats[5]['holders'] = 82;
$cats[6]['holders'] = -3;
$cats[7]['holders'] = -5;
$cats[8]['holders'] = -17;
$cats[9]['holders'] = -25;
$cats[10]['holders'] = 66;
$cats[11]['holders'] = -10;
$cats[12]['holders'] = 0;
$cats[13]['holders'] = 5;
$cats[14]['holders'] = 4;
$cats[15]['holders'] = -3;
function compareHolders($a, $b) {
$aPoints = $a['holders'];
$bPoints = $b['holders'];
return strcmp($aPoints, $bPoints);
}
$cats = usort($cats, 'compareHolders');
I would like to get the top 5 values and bottom 5 values:
$first_5_tokens = array_slice($tokens, 0, 5, true);
print_r($first_5_tokens);
$last_5_tokens = array_slice($tokens, -5);
print_r($last_5_tokens);
This is not sorting the array for me by "holder" value. How can I do this? Thanks!

Answer 1

Your comparison function sorts array in descending order and also, don't use it like - $cats = usort($cats, 'compareHolders'); Instead just use it like - usort($cats, 'compareHolders');
I changed your function and did it like this.
$cats[0]['holders'] = 55;
$cats[1]['holders'] = 66;
$cats[2]['holders'] = 77;
$cats[3]['holders'] = 23;
$cats[4]['holders'] = 64;
$cats[5]['holders'] = 82;
$cats[6]['holders'] = -3;
$cats[7]['holders'] = -5;
$cats[8]['holders'] = -17;
$cats[9]['holders'] = -25;
$cats[10]['holders'] = 66;
$cats[11]['holders'] = -10;
$cats[12]['holders'] = 0;
$cats[13]['holders'] = 5;
$cats[14]['holders'] = 4;
$cats[15]['holders'] = -3;
foreach($cats as $cat) {
echo $cat['holders'] . "<br>";
}
// function compareHolders($a, $b) {
//
// $aPoints = $a['holders'];
// $bPoints = $b['holders'];
//
// return strcmp($aPoints, $bPoints);
//
// }
function compareHolders($a, $b) {
$a = $a['holders'];
$b = $b['holders'];
if ($a == $b)
return 0;
return ($a > $b) ? -1 : 1;
}
usort($cats, 'compareHolders');
echo "<h4>After</h4>\n";
foreach($cats as $cat) {
echo $cat['holders'] . "<br>";
}
// print_r($cats);
$tokens = $cats;
echo "<h4>First Five</h4>\n";
$first_5_tokens = array_slice($tokens, 0, 5, true);
print_r($first_5_tokens);
echo "<h4>Last Five</h4>\n";
$last_5_tokens = array_slice($tokens, -5);
print_r($last_5_tokens);