protected function generateVerifyCode()
{
if ($this->minLength > $this->maxLength) {
$this->maxLength = $this->minLength;
}
if ($this->minLength < 3) {
$this->minLength = 3;
}
if ($this->maxLength > 20) {
$this->maxLength = 20;
}
$length = mt_rand($this->minLength, $this->maxLength);
$letters = 'bcdfghjklmnpqrstvwxyz';
$vowels = 'aeiou';
$code = '';
for ($i = 0; $i < $length; ++$i) {
if ($i % 2 && mt_rand(0, 10) > 2 || !($i % 2) && mt_rand(0, 10) > 9) {
$code .= $vowels[mt_rand(0, 4)];
} else {
$code .= $letters[mt_rand(0, 20)];
}
}
return $code;
}