向变量添加/减去随机数

Question

I want to create some random sql data with a php script

currently I get the last record, generate a random number between 1 and 2 ... if its a 1 I will add a random number to the record else if its a 2 i will subtract a random number from

the problem is it keeps spitting out minus random numbers! I only want positive random numbers.

$result = mysql_query("SELECT * FROM Data ORDER BY id DESC") 
    or die(mysql_error()); 

while($row = mysql_fetch_array( $result )) {
// Print out the contents of each row into a table

    $temp=$row['temp'];
    $light=$row['light'];

};

$name="Herbi";
$date=Date("o:m:d");
$time=Date("H:i:s");

$rand =rand(1,2);
$randnu =rand(1,10);

echo " rand:".$rand;
switch($rand){

    case 1:
        $temprand=$temp+$randnu;
        $lightrand=$light+$randnu;
    break;

    case 2:
        $temprand=$temp-$randnu;
        $lightrand=$light-$randnu;
    break;
};
echo"";
echo"randnu";
echo $randnu;
echo "   ";
echo"lightrand";
echo $lightrand;

Answer 1

Based on your code this is valid, if your $temp=1 and $rand=2 then $temprand will be -1.

You can add a check that your $temp and $light should always be greater than or equal the max random numbers so when you minus the (max of) random number from $temp or $light you will end up with 0.

if($row['temp']>=2){
  $temp=$row['temp'];
}else{
  $temp=2; //Max of $rand =rand(1,2);
}

or shorthand

$temp=($row['temp'] >= 2? $row['temp'] : 2);
$light=($row['light'] >= 10? $row['light'] : 10);