php array - search for random key where value is over 0

Question

I have a php array that's made up of random numbers from 0-100.

I'm trying to figure out the cleanest and simplest method of picking a random key from that array that is greater than zero. Ultimately I'm looping through the array, subtracting a value from random keys each loop

Pseudo code:

$num_array = array(100,50,60,40,0,30,0,20);

for ($x = 0; $x < 100; $x++) {
    $rnd = RANDOM $num_array KEY WHERE > 0  
    $num_array[$rnd] = $num_array[$rnd] - 10;
}

Any suggestions on how to handle this?

EDIT: Once the loop is over I still want my array to contain 0's (originals, and any new ones after subtraction), and all the key positions need to be intact as before

Answer 1

1st : simple apply array_filter it will filter zeros from array

2nd : Apply array_rand function

<?php

$nums = [70, 100, 40, 30, 0, 45, 10];

$new_nums = array_filter($nums);

$key = array_rand($new_nums , 1);

echo $new_nums [$key];

?>

Answer 2

I would suggest to first remove the zeroes, and only then pick a random value:

$nums = [70, 100, 40, 30, 0, 45, 10];
$temp = array_values(array_filter($nums));
$random = $temp[mt_rand(0, count($temp) - 1)];

NB: random value is selected according to user comment on the PHP documentation page.