Why is the array empty after this code is executed?

Get the code first

<code>$suffix = 0; //用户ID尾数
$ids = [];
$stores = [1,10,23,45,67,56,45,324,23]; //储存用户ID的数组
$limit = 5;
$count = count($stores);
$i=0;
do{
    $id = $stores[array_rand($stores ,1)];
    $sub = substr($id ,-1);
    if($sub==$suffix){
        $ids[$id] = $id;
    }
    $i++;
}while(count($ids)<$limit && $i<$count);
print_r($ids);
exit;</code>

I want to get user IDs ending in 0 from $stores. The maximum number is 5 and the minimum number is 1. The result is stored in an array. I have the above code
, but when I execute it, there are $ids as When empty. . . Don't understand. . .

Reply content:

Get the code first

<code>$suffix = 0; //用户ID尾数
$ids = [];
$stores = [1,10,23,45,67,56,45,324,23]; //储存用户ID的数组
$limit = 5;
$count = count($stores);
$i=0;
do{
    $id = $stores[array_rand($stores ,1)];
    $sub = substr($id ,-1);
    if($sub==$suffix){
        $ids[$id] = $id;
    }
    $i++;
}while(count($ids)<$limit && $i<$count);
print_r($ids);
exit;</code>

I want to get user IDs ending in 0 from $stores. The maximum number is 5 and the minimum number is 1. The result is stored in an array. I have the above code
, but when I execute it, there are $ids as When empty. . . Don't understand. . .

Why do you need to use while and the data looped through is still a random element of the array? Can't you use foreach?

If the result is not empty, try this

<code>        $suffix = 0; //用户ID尾数
        $ids = [];
        $stores = [1,10,23,45,67,56,45,324,23]; //储存用户ID的数组
        $limit = 5;
        $count = count($stores);
        $i=0;
        do{
            $id = $stores[array_rand($stores ,1)];
            $sub = substr($id ,-1);
            if($sub==$suffix){
                $ids[$id] = $id;
            }
            $i++;
            $iCount = count($ids);
        }while($iCount == 0 || ($count<$limit && $i<$count ));
        print_r($ids);
        exit;</code>

No matter how many times you run array_rand($stores,1), there may be array elements that can never be retrieved.
$stores with a mantissa of 0 is only 10;
$count = count($stores); means do_while at most 10 times.

If you don’t get the number 10 after 10 times, you will only get an empty array in the end.

<code><?php

$suffix = 0; //用户ID尾数
$ids = [];
$stores = [1,10,23,45,67,56,45,324,23]; //储存用户ID的数组
$limit = 5;
$count = count($stores);
$i = 0;
do {
    $id = $stores[array_rand($stores, 1)];
    $sub = substr($id, -1);
    echo 'test:'.$id."\n";
    if ($sub == $suffix) {
        $ids[$id] = $id;
        echo 'got:'.$id."\n";
    }
    ++$i;
    echo 'count($ids):'.count($ids)."\n";
    echo '$i:'.$i."\n";

} while (count($ids) < $limit && $i < $count);
print_r($ids);</code>

The result is empty:

<code>[root@localhost www]# php test.php
test:1
count($ids):0
$i:1
test:23
count($ids):0
$i:2
test:23
count($ids):0
$i:3
test:56
count($ids):0
$i:4
test:45
count($ids):0
$i:5
test:67
count($ids):0
$i:6
test:324
count($ids):0
$i:7
test:67
count($ids):0
$i:8
test:67
count($ids):0
$i:9
Array
(
)</code>

The result is not empty:

<code>[root@localhost www]# php test.php
test:324
count($ids):0
$i:1
test:10
got:10
count($ids):1
$i:2
test:23
count($ids):1
$i:3
test:10
got:10
count($ids):1
$i:4
test:67
count($ids):1
$i:5
test:324
count($ids):1
$i:6
test:45
count($ids):1
$i:7
test:45
count($ids):1
$i:8
test:1
count($ids):1
$i:9
Array
(
    [10] => 10
)</code>