生成随机数并保存在数据库中

On my PHP/MYSQL BASED website sellers can post 10 items of the same kind and nature and value.

I want users to be able to post qty = 10, value = 100. (values are preset in a dropdown and selected by sellers).

At the moment I am able to post a single item only for a preset value and a code is generated as shown in the code given below:

 $sql_query = "INSERT INTO 
 eg_posts(seller_id,value_id,quantity,cdate,egcode) 
 VALUES
 ('$a','$bval','$cqty',now(),CONCAT( CHAR(FLOOR(RAND()*26)+65),FLOOR(100+RAND()*(5000-100))))"; 

The above post is saved with one item, with one alphanumeric code with a preset value chosen by the seller.

I want the user to be able to post more than one items (say 10) of the same kind and nature and value and I want 10 random alphanumeric codes to be generated for these 10 items. And I want all 10 random codes to be save in the database under the post ID.

Using PDO (it will work even if you want to change the values for different values, quantities because it binds each variable separately):

try {
    //Make your connection handler to your database
    $conn = new PDO("mysql:host=".$servername.";dbname=".$database, $username, $password, array(PDO::ATTR_ERRMODE => PDO::ERRMODE_WARNING));
    $a = 1;
    $bval= 1;
    $cqty = 10;

    $values = array();
    $binds = array();

    $temp = "INSERT INTO eg_posts (seller_id, value_id, quantity, cdate, egcode) VALUES ";

    for($i = 0; $i < 10; $i ++) {
        $values[] = ' (seller_id'.$i.' = :seller_id'.$i.', value_id'.$i.' = :value_id'.$i.', quantity'.$i.' = :quantity'.$i.', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) )))';
        $binds[':seller_id'.$i] = $a;
        $binds[':value_id'.$i] = $bval;
        $binds[':quantity'.$i] = $cqty;
    }
    $sql_query = $temp.implode(', ', $values).';';

    $stmt = $conn->prepare($sql_query);
    $stmt->execute($binds);

} catch(PDOException $e) {
    echo $e->getMessage();
    die();
}

Result:

INSERT INTO eg_posts (seller_id, value_id, quantity, cdate, egcode) 
VALUES 
(seller_id0 = :seller_id0, value_id0 = :value_id0, quantity0 = :quantity0, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id1 = :seller_id1, value_id1 = :value_id1, quantity1 = :quantity1, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id2 = :seller_id2, value_id2 = :value_id2, quantity2 = :quantity2, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id3 = :seller_id3, value_id3 = :value_id3, quantity3 = :quantity3, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id4 = :seller_id4, value_id4 = :value_id4, quantity4 = :quantity4, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id5 = :seller_id5, value_id5 = :value_id5, quantity5 = :quantity5, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id6 = :seller_id6, value_id6 = :value_id6, quantity6 = :quantity6, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id7 = :seller_id7, value_id7 = :value_id7, quantity7 = :quantity7, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id8 = :seller_id8, value_id8 = :value_id8, quantity8 = :quantity8, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
(seller_id9 = :seller_id9, value_id9 = :value_id9, quantity9 = :quantity9, NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) )));

Plain SQL:

$a = 1;
$bval= 1;
$cqty = 10;

$temp = "INSERT INTO eg_posts (seller_id, value_id, quantity, cdate, egcode) VALUES ";
$values = array();
for($i = 0; $i < 10; $i ++) {
    $values[] = " ('$a', '$bval', '$cqty', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) )))";
}
$sql_query = $temp.implode(', ', $values).';';

echo $sql_query;

Result:

INSERT INTO eg_posts (seller_id, value_id, quantity, cdate, egcode) 
VALUES 
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) ))),
('1', '1', '10', NOW(), CONCAT( CHAR(FLOOR(RAND()*26) + 65), FLOOR(100 + RAND() * (5000-100) )));