$arr = array ('asfsdg','t3hbwed','gwefa@','43fsd4');
$string = $arr[array_rand($arr)];

a, b, ab, ba, aa, bb

a, b, 1, ab1, 1ab, ba1, etc ...

1ad@cb2#

function getToken($length = 10) {
    $alphanum = str_split('abcdefghijklmnopqrstuvwxyz0123456789-_',1);
    $token = '';
    while (strlen($token) <= $length) {
      $token .= $alphanum[array_rand($alphanum)];
    }
    return $token;
}

function getTokens($length = 10, $count = 3) {
    $alphanum = str_split('abcdefghijklmnopqrstuvwxyz0123456789-_',1);
    $output = array();
    while (count($output) <= $count) {
        $token = '';
        while (strlen($token) <= $length) {
          $token .= $alphanum[array_rand($alphanum)];
        }
        if (!in_array($output,$token)) {
          $output[] = $token;
        }
    }
    return $output;
}

<?php

echo 's'.date('Ymdhis').'<br>';
echo 's'.time('his');

?>

bin2hex(openssl_random_pseudo_bytes(256))

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