Assignment Operator_PHP Tutorial

The basic assignment operator is "=". You tend to think it means "equal to". Don't think of it this way, what it really means is that the operand on the left gets the value of the expression on the right.
The significance of an assignment expression lies in the assignment of values. In other words, the value of "$a=3" is 3. This allows you to do things like:

$a = ($b = 4) + 5;
// $a is equal to 9 now, and $b has been set to 4.
　
As a complement to the assignment operator, there is also a combination operator that operates on binary numbers and character strings. This operator allows you to use the value of the assigned expression on the assignment side. For example:
　
$a = 3;
$a += 5; // sets $a to 8, as if we had said: $a = $a + 5;
$b = "Hello ";
$b .= "There!"; // sets $b to "Hello There!", just like $b = $b . "There!";