How to generate random numbers or OTP with function in PHP?

Generate random numbers or OTP with function in PHP

function generateNumericOTP($n=6) { 

   $generator = "1357902468"; 

   $result = "";  

   for ($i = 1; $i <= $n; $i++) {  

   $result .= substr($generator, (rand()%(strlen($generator))), 1);   

   } 

   return $result;

   }  

 

generateNumericOTP(4);