One-line PHP random string generator?

Question

I am looking for the shortest way to generate random/unique strings and for that I was using the following two:

$cClass = sha1(time());

or

$cClass = md5(time());

However, I need the string to begin with a letter, I was looking at base64 encoding but that adds == at the end and then I would need to get rid of that.

What would be the best way to achieve this with one line of code?

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Update:

PRNDL came up with a good suggestions which I ended up using it but a bit modified

echo substr(str_shuffle(abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ),0, 1) . substr(str_shuffle(aBcEeFgHiJkLmNoPqRstUvWxYz0123456789),0, 31)

Would yield 32 characters mimicking the md5 hash but it would always product the first char an alphabet letter, like so;

However, Uours really improved upon and his answer;

substr(str_shuffle("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), 0, 1).substr(md5(time()),1);

is shorter and sweeter

The other suggestion by Anonymous2011 was very awesome but the first character for some reason would always either M, N, Y, Z so didn't fit my purposes but would have been the chosen answer, by the way does anyone know why it would always yield those particular letters?

Here is the preview of my modified version

echo  rtrim(base64_encode(md5(microtime())),"=");

question from:https://stackoverflow.com/questions/19017694/one-line-php-random-string-generator

Answer 1

Rather than shuffling the alphabet string , it is quicker to get a single random char .

Get a single random char from the string and then append the md5( time( ) ) to it . Before appending md5( time( ) ) remove one char from it so as to keep the resulting string length to 32 chars :

substr("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ", mt_rand(0, 51), 1).substr(md5(time()), 1);

Lowercase version :

substr("abcdefghijklmnopqrstuvwxyz", mt_rand(0, 25), 1).substr(md5(time()), 1);

Or even shorter and a tiny bit faster lowercase version :

chr(mt_rand(97, 122)).substr(md5(time()), 1);

/* or */

chr(mt_rand(ord('a'), ord('z'))).substr(md5(time()), 1);

A note to anyone trying to generate many random strings within a second:
Since time( ) returns time in seconds , md5( time( ) ) will be same throughout a given second-of-time due to which if many random strings were generated within a second-of-time, those probably could end up having some duplicates .

I have tested using below code . This tests lower case version :

    $num_of_tests = 100000;

    $correct = $incorrect = 0;

    for( $i = 0; $i < $num_of_tests; $i++ )
    {
        $rand_str = substr( "abcdefghijklmnopqrstuvwxyz" ,mt_rand( 0 ,25 ) ,1 ) .substr( md5( time( ) ) ,1 );

        $first_char_of_rand_str = substr( $rand_str ,0 ,1 );

        if( ord( $first_char_of_rand_str ) < ord( 'a' ) or ord( $first_char_of_rand_str ) > ord( 'z' ) )
        {
            $incorrect++;
            echo $rand_str ,'<br>';
        }
        else
        {
            $correct++;
        }
    }

    echo 'Correct: ' ,$correct ,' . Incorrect: ' ,$incorrect ,' . Total: ' ,( $correct + $incorrect );