what does the the -= operator do

It sets the value on the left to be itself minus the value on the right (for example, i-=3 is the same as i = i-3). It’s called the subtraction-assignment operator.

By Clinton Montague

Posts by Clinton Montague
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The -= operator is a simplified way of writing I want to decrease the variable by a certain value. It’s called the subtraction-assignment operator.

Examples

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$i = 10;
$i-=1;
echo $i; // outputs 9;
 
$i = 10;
$i-=5;
echo $i; // outputs 5
 
$i=10;
$i-= -10;
echo $i; // output 20 (since 10 - (-10) is the same as 10+10;
 
$i=10;
$i-=$i;
echo $i; // output 0;

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