string - Replace first and last digit with * in php -

i want replace 1st , last digit of number series *. such have

$number = 123435987345735372;  

i want such

*535738753957353*  

like this?

$number = 123435987345735372;  $new_number = substr($number, 1, -1); $new_number = "*".$new_number."*"; echo"original number: $number<br>new number: $new_number"; 

like norbert van nobelen said, check out manual @ php.net