PHP realizes user defined function sharing of the middle four digits of mobile phone number hidden by asterisk (*)

Middle 4 digits of php shielded telephone number:

Method 1 : 

function hidtel($phone){

    $IsWhat = preg_match('/(0[0-9]{2,3}[\-]?[2-9][0-9]{6,7}[\-]?[0-9]?)/i',$phone); // Fixed telephone 

    if($IsWhat == 1){

        return preg_replace('/(0[0-9]{2,3}[\-]?[2-9])[0-9]{3,4}([0-9]{3}[\-]?[0-9]?)/i','$1****$2',$phone);

    }else{

        return  preg_replace('/(1[358]{1}[0-9])[0-9]{4}([0-9]{4})/i','$1****$2',$phone);

    }

}
Method 2 : 

$num = "13966778888"

$str = substr_replace($num,'****',3,4);

Example:

$phonenum = "13966778888";

echo hidtel($phonenum);

Final output: 139****8888