Page 80 - Beginning PHP 5.3

Part II: Learning the Language
which means: “ Assign the value 8.23 to $test_var , then assign the result of that expression ( 8.23 ) to
$another_var . ” So both $test_var and $another_var now contain the value 8.23 .

The equals sign ( = ) can be combined with other operators to give you a combined assignment operator that
makes it easier to write certain expressions. The combined assignment operators (such as +=, – =, and so
on) simply give you a shorthand method for performing typical arithmetic operations, so that you don ’ t
have to write out the variable name multiple times. For example, you can write:
$first_number += $second_number;

rather than:

$first_number = $first_number + $second_number;
This also works for other kinds of operators. For example, the concatenation operator (described later
in this chapter) can be combined with the equals sign (as .= ), causing the value on the right side to be
appended to the existing value on the left, like this:

$a = “Start a sentence “;
$b = “and finish it.”;
$a .= $b; // $a now contains “ Start a sentence and finish it. ”

The main arithmetic, string, and bitwise operators support combination in this fashion; find out more at
.
http://www.php.net/manual/en/language.operators.assignment.php
Bitwise Operators
PHP ’ s bitwise operators let you work on the individual bits within integer variables. Consider the
integer value 1234. For a 16 - bit integer, this value is stored as two bytes: 4 (the most significant byte) and
210 (the least significant). 4 * 256 + 210 = 1234.

Here ’ s how those two bytes look as a string of bits:
00000100 11010010

A bit with a value of 1 is said to be set , whereas a bit with a value of 0 is unset (or not set).

PHP ’ s bitwise operators let you manipulate these bits directly, as shown in the following table.
Each example includes both decimal values and their binary equivalents, so you can see how the bits
are altered:

Operator Description Example
& (And) Only bits set in both values 14 & 3 = 2
are set in the result 00001110 & 00000011 = 00000010
| (Or) Bits set in either value are set 14 | 3 = 15
in the result 00001110 | 00000011 = 00001111

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