PHP未定义变量，但脚本工作正常，如果我定义变量它不起作用[关闭]

I have a problem with an undefined variable, if I define the variable the script does not work correctly, I know it's a simple answer I just can't find it.

Here is my code: ( I use this in a for each loop )

$weight= ($item['weight']*$item['quantity']);  
$totalweight = ($totalweight + $weight) 

echo $totalweight;

The script works perfect and gives me the correct answerexcept I get an undefined variable error on line 2 $totalweight

I have tried to set the variable it then breaks the calculation.

You need to initialize the variable outside of the loop so it's not overwritten on every iteration:

$totalweight = 0;
foreach ($items as $item) {
    $weight= ($item['weight']*$item['quantity']);  
    $totalweight = ($totalweight + $weight) 
}

echo $totalweight;

How are you setting the variable? PHP is producing this notice because you are asking it to add $totalWeight and $weight and it doesn't know what $totalWeight is.

To remove this notice you could do:

$totalWeight = 0;
$weight= ($item['weight']*$item['quantity']);  
$totalweight = ($totalweight + $weight);

echo $totalweight;

Although it's probably just best to change the line to be:

$totalweight = $weight;

(Unless of course this code runs in a loop or the like).