Using unique random numbers for a switch statement - php

Question

I need a function or an array that gives me random numbers from 1 - 47, so I can use it for my code below.
public function output($question_id, $solution) {
$yes = ($GLOBALS['TSFE']->sys_language_uid == 0) ? 'Ja' : 'Oui';
$no = ($GLOBALS['TSFE']->sys_language_uid == 0) ? 'Nein' : 'No';
switch ($question_id) {
case 1:
$arg = array(
'main_content' => $this->build_html(1, '01_0429_04_14_Psori_Arthro.jpg', $yes, $no, $solution)
);
break;
case 2:
$arg = array(
'main_content' => $this->build_html(2, '02_0342_05_14_Psori_Arthropathie.jpg', $yes, $no, $solution),
);
break;
case 3:
$arg = array(
'main_content' => $this->build_html(3, '03_0255_05_14_Psori_Arthropathie.jpg', $yes, $no, $solution),
);
break;
}
}
Example
This
case 1:
$arg = array(
'main_content' => $this->build_html(1, '01_0429_04_14_Psori_Arthro.jpg', $yes, $no, $solution)
);
should look somehow like this:
case $random_id:
$arg = array(
'main_content' => $this->build_html($random_id, '01_0429_04_14_Psori_Arthro.jpg', $yes, $no, $solution)
);
So that means, each case and each first parameter of the function build_html should get a unique random id.
Of course I could use rand() but then it is quite possible that I get duplicated values.
Any help would be appreciated!

Answer 1

Create a class like follows:
class SamplerWithoutReplacement {
private $pool;
public __construct($min,$max) {
$this->pool = range($min,$max);
}
public function next() {
if (!empty($this->pool)) {
$nIndex = array_rand($this->pool);
$value = $this->pool[$nIndex];
unset($this->pool[$nIndex]);
return $value;
}
return null; //Or throw exception, depends on your handling preference
}
}
Use it as:
$sampler = new SamplerWithoutReplacement(1,47);
//do things
$value = $sampler->next();
The $sampler will draw random samples between 1-47 without replacing them in the pool and therefore they'll be unique.

Answer 2

Not tested but I think it should work:
$numbers = [];
function genenerate_nr_not_in_list($list, $min = 1, $max = 47) {
$number = rand($min, $max);
while (false !== array_search($number, $list)) {
$number = rand($min, $max);
}
return $number;
}
for ($i = 0; $i < 47; $i++) {
$numbers[] = genenerate_nr_not_in_list($numbers);
}
With this solution you can generate numbers in each range ($min and $max parameters). But it should be at least as big as the number of values you need ($max).