我怎样才能给变量赋值？

Question

I am trying to make some function but, i am getting white page result when i put -ve value for $variable. Look this variable has -ve value : $long_total_profit_loss = "-900";

$long_total_profit_loss = "-900";
$short_sell_total_profit_loss = "-600";

//CONCLUTION
if(($long_total_profit_loss > $short_sell_total_profit_loss) && ($long_total_profit_loss>0)){

    echo "long has higher in profit";
}elseif (($long_total_profit_loss > $short_sell_total_profit_loss) && ($long_total_profit_loss < 0)){

    echo "long has higher loss";
}elseif (($long_total_profit_loss < $short_sell_total_profit_loss) && ($long_total_profit_loss > 0)){

    echo "short has higher in profit";
}
elseif (($long_total_profit_loss > $short_sell_total_profit_loss) && ($long_total_profit_loss < 0)){

    echo "short has higher loss";
}

Answer 1

I'd recommend to structure your conditions differently (with nested if statements), which will give you a better overview and readability so you can't forget a special situation.

$long_total_profit_loss = -900;
$short_sell_total_profit_loss = -600;

if($long_total_profit_loss > $short_sell_total_profit_loss) {
   if($long_total_profit_loss > 0) {
     echo "long has higher in profit";
   }
   else { // $long_total_profit_loss<0 or =0
     echo "short has higher loss";
   }
}
else { // $long_total_profit_loss < $short_sell_total_profit_loss or equal
   if($short_sell_total_profit_loss > 0) {
      echo "short has higher in profit";
   }
   else {  // $short_sell_total_profit_loss<0 or =0
      echo "long has higher loss";
   }
}

// output: short has higher loss

You could/should extend this to capture the case when those values are equal to each other and equal to 0.

EDIT
swapped wording of "short has higher loss" and "long has higher loss", which makes more sense, thanks to @Rafael