PHP loop creating duplicate database rows

Question

I'm playing about creating a database that contains plaintext and hash values for any combination of passwords, however when they are added to the database I end up with many duplicates before it moves on to the next combination... Any ideas as to why and how to stop it?

<?php
$con=mysqli_connect("localhost","root","","test");
// Check connection
if (mysqli_connect_errno())
{
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

$numberof=0;
$alphabet = array("A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z");

for($i=0; $i<count($alphabet); $i++){
    for($j=0; $j<count($alphabet); $j++){
        for($k=0; $k<count($alphabet); $k++){
            for($l=0; $l<count($alphabet); $l++){
                $final = $alphabet[$i].$alphabet[$j].$alphabet[$k];
                $hash = md5($final);

                mysqli_query($con,"INSERT INTO hashes (plain, hash) VALUES ('$final', '$hash')");
            }
        }
    }
}
echo $numberof;
?>

You are not adding the $alphabet[$l] to your $final string. — Hidde
– Hidde, Commented Jul 25, 2013 at 12:04
Just as an information : Because md5 generates a string of a fixed length duplicate hashes are possible — DarkBee
– DarkBee, Commented Jul 25, 2013 at 12:05
Of course! They're not duplicates, they're just missing the 4th letter! Duuuuh!! :P Thanks, Hidde :) — Steve
– Steve, Commented Jul 25, 2013 at 12:05
To create $alphabet array you can use range. Like range('A','Z'); — som
– som, Commented Jul 25, 2013 at 12:38

ಠ_ಠ · Accepted Answer · 2013-07-25 12:05:17Z

1

You have four nested for loops, with counters $i $j $k and $l. However, your final string that you use in your query only uses $i $j and $k So you'll have about 26 duplicates. I assume you meant to append the value of $l to the end of your string?

answered Jul 25, 2013 at 12:05

ಠ_ಠ

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2 Comments

Steve Over a year ago

Second problem, after 30 seconds of generation it has an error, I'm guessing because MySQL needs to finish whatever within 30 seconds... any way around that?

ಠ_ಠ Over a year ago

For PHP itself, you can use ini_set('max_execution_time', ###);, but there may be other limitations put in place on the server that you're hosting this on.

Dhaval Bharadva · Accepted Answer · 2013-07-25 12:33:48Z

0

just remove the last loop. i have update your code as below:

for($i=0; $i<count($alphabet); $i++){
    for($j=0; $j<count($alphabet); $j++){
        for($k=0; $k<count($alphabet); $k++){
            $final = $alphabet[$i].$alphabet[$j].$alphabet[$k];
            $hash = md5($final);
            mysqli_query($con,"INSERT INTO hashes (plain, hash) VALUES ('$final', '$hash')");           
        }
    }
}

answered Jul 25, 2013 at 12:33

Dhaval Bharadva

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