PHP shortcuts for math operator plus assignment operator

http://www.daaq.net/old/php/index.php?page=php+math+operators&parent=php+expressions

PHP also allows another type of operator that perform with is called assignment with operation. What this means is that they include both a math operator and an assignment operator in one operation. What is the purpose of such an operator? Well, many expressions you will end up writing may take the form of $a = $a + $b;, or the value of the first operand equals the value of the first operand as modified by a second operand. PHP allows a shorthand notation for these. $a = $a + $b; is equivalent to $a += $b. The same shortcut can be applied to subtraction, multiplication, division and modulus.

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Note that in each of these, the two characters form a single operator, and cannot have a space between them.

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