Page 83 - Beginning PHP 5.3

Chapter 3: PHP Language Basics
The location of the operators makes a difference. Placing the operator before the variable name causes the
variable ’ s value to be incremented or decremented before the value is returned; placing the operator after
the variable name returns the current value of the variable first, then adds or subtracts one from the
variable. For example:

$x = 5;
echo ++$x; // Displays “6” (and $x now contains 6)
$x = 5;

echo $x++; // Displays “5” (and $x now contains 6)

Interestingly, you can use the increment operator with characters as well. For example, you can “ add ”
one to the character B and the returned value is C. However, you cannot subtract from (decrement)
character values.
Logical Operators
PHP ’ s logical operators work on Boolean values. Before looking at how logical operators work, it ’ s
worth taking a bit of time to explore Boolean values more thoroughly.

As you ’ ve already seen, a Boolean value is either true or false . PHP automatically evaluates
expressions as either true or false when needed, although as you ’ ve already seen, you can use
settype() or casting to explicitly convert a value to a Boolean value if necessary.

For example, the following expressions all evaluate to true :
1
1 == 1
3 > 2

“hello” != “goodbye”
The following expressions all evaluate to false :

3 < 2
gettype( 3 ) == “array”
“hello” == “goodbye”

In addition, PHP considers the following values to be false :
❑ The literal value false

❑ The integer zero ( 0 )
❑ The float zero ( 0.0 )
❑ An empty string ( “ “ )
❑ The string zero ( “0” )
❑ An array with zero elements
❑ The special type null (including any unset variables)
❑ A SimpleXML object that is created from an empty XML tag (more on SimpleXML in Chapter 19 )
All other values are considered true in a Boolean context.

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