PHP生成没有特定前缀的随机数？

Question

I want to generate a random 9 character long integer.
I also want to make sure the first 3 digits aren't 814.
This is what I came up with so far:

Function to generate number:

public function randnum(){
$random = substr(number_format(time() * rand(),0,'',''),0,9);
return $random
}

Where I want to get the number at.

$random;
while ((substr(randnum(),0,3)) == '814'){
$random=substr(randnum(),0,3));
}

Is this the right way to ensure the number I get does not start with 814?

Answer 1

do {
    $random = mt_rand(100000000, 999999999);
} while (strpos($random, '814') === 0);