php only first digit in mySQL-CodePudding

I am trying to output randomly generated values via "echo" command and write them to a database. The "echo" output is no problem, but in the mySQL table only the first digit of the generated number is given. In theory there should be displayed five digits. https://i.stack.imgur.com/1KPGi.png

if ($submitbutton){
    $length = 5;
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz@#$&*";  
    $size = strlen( $chars );  
    echo "Key: ";  
    for( $i = 0; $i < $length; $i   ) {  
        $str= $chars[ rand( 0, $size - 1 ) ];  
        echo $str; 
        $sql = "INSERT INTO regkey (regkey) VALUES (?)";
        $stmt = mysqli_prepare($link, $sql);
        $str1 = $str;
        mysqli_stmt_bind_param($stmt, "s", $str1);
        mysqli_stmt_execute($stmt);
        mysqli_stmt_close($stmt);
        mysqli_close($link);
    }

If I try to enter another predefined value via php, this works without problems.

CodePudding user response：

This is nothing to do with your database.

In your for loop, you overwrite $str with a single character every time the loop runs. I guess you intended to append to it instead using .=. (N.B. This logical flaw is masked by the fact you echo within the loop, so on screen you see what looks like a single string but is in fact 5 separate strings right next to each other.)

You then also run the INSERT the same number of times, so you get 5 separate entries, one for each digit (although since you close the connection within the loop and then don't re-open it, it's hard to see how that is actually succeeding - I'd guess the 2nd query fails and you either didn't mention the error or have suppressed all error reporting so you didn't see it).

It was little unclear, but I think you wanted to generate one 5-digit string and write it all to the same row in the database? If so, then do it like this:

if ($submitbutton){
    $length = 5;
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz@#$&*";  
    $size = strlen( $chars );  
    echo "Key: ";
    $str = "";
    
    for( $i = 0; $i < $length; $i   ) {  
        $str .= $chars[ rand( 0, $size - 1 ) ];  //append not overwrite
    }
    
    //after the loop has finished, do the echo and insert once only
    echo $str; 
    $sql = "INSERT INTO regkey (regkey) VALUES (?)";
    $stmt = mysqli_prepare($link, $sql);
    mysqli_stmt_bind_param($stmt, "s", $str);
    mysqli_stmt_execute($stmt);
    mysqli_stmt_close($stmt);
    mysqli_close($link);

N.B. As suggested in the comments, you could also replace the for loop entirely with

$str = substr(str_shuffle($chars), 0, $length);

which will do the same job for you using existing PHP functions.