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copied!<p>I like this method of generating a cryptographically secure pseudo-random number generator or (CSPRNG) for PHP. It was <a href="https://stackoverflow.com/questions/1846202/php-how-to-generate-a-random-unique-alphanumeric-string/13733588#13733588">written by Scott</a>:</p> <pre><code><?php function crypto_rand_secure($min, $max) { $range = $max - $min; if ($range < 0) return $min; // not so random... $log = log($range, 2); $bytes = (int) ($log / 8) + 1; // length in bytes $bits = (int) $log + 1; // length in bits $filter = (int) (1 << $bits) - 1; // set all lower bits to 1 do { $rnd = hexdec(bin2hex(openssl_random_pseudo_bytes($bytes))); $rnd = $rnd & $filter; // discard irrelevant bits } while ($rnd >= $range); return $min + $rnd; } function getToken($length=32){ $token = ""; $codeAlphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; $codeAlphabet.= "abcdefghijklmnopqrstuvwxyz"; $codeAlphabet.= "0123456789"; for($i=0;$i<$length;$i++){ $token .= $codeAlphabet[crypto_rand_secure(0,strlen($codeAlphabet))]; } return $token; } ?> </code></pre> <p>In terms of adding a timeout, I recommend taking care of this in the database. Add a column that is called like registration_timeout and then use mysql's addtime() function to set this colmn to the current time stamp + however long you want the timeout to be.</p> <p>Also keep in mind that temporary email accounts are trivial to use (<a href="http://www.mailinator.com" rel="nofollow noreferrer">http://www.mailinator.com</a> , <a href="http://www.guerrillamail.com" rel="nofollow noreferrer">http://www.guerrillamail.com</a>, ect...), so asking for someone to register an email account doesn't mean anything. Further more a user account could end up on <a href="http://www.bugmenot.com" rel="nofollow noreferrer">http://www.bugmenot.com</a> . </p>

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