Examples

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$i = 10;
$i+=1;
echo $i; // outputs 11;
 
$i = 10;
$i+=5;
echo $i; // outputs 15
 
$i=10;
$i+= -10;
echo $i; // output 0 (since 10 + (-10) is the same as 10-10);
 
$i=10;
$i+=$i;
echo $i; // output 20;

Find out more

• MSDN page about the addition assignment for JScript
• Google search for “addition-assignment”
• A post by me: Operator precedence – what does (i=1)*i-- - --i*(i=-3)*i++ + ++i equal and why? (not for beginners)
• A similar FQG – What does the -= operator do?

They all sound like stupid questions if you know what the answer is, but all questions do, don’t they? I have decided to start a series of quick posts answering some of the more obscure search terms that cause people to arrive at this site. Hopefully you might even find some of them useful.

The posts won’t get in the way of normal blog posts, they’ll be exclusively posted in the fgq section, but they’ll still appear in the feed so remember subscribe to that to keep up to date.

Take me to the new FGQ section!