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Incrementing/Decrementing Operators

PHP supports C-style pre- and post-increment and decrement operators.

Note: The increment/decrement operators do not affect boolean values. Decrementing NULL values has no effect too, but incrementing them results in 1.

**Increment/decrement Operators**
Example	Name	Effect
++$a	Pre-increment	Increments $a by one, then returns $a.
$a++	Post-increment	Returns $a, then increments $a by one.
--$a	Pre-decrement	Decrements $a by one, then returns $a.
$a--	Post-decrement	Returns $a, then decrements $a by one.

Here's a simple example script:

  <?php 
 echo  "<h3>Postincrement</h3>" ; 
 $a  =  5 ; 
echo  "Should be 5: "  .  $a ++ .  "<br />\n" ; 
echo  "Should be 6: "  .  $a  .  "<br />\n" ; 
 
echo  "<h3>Preincrement</h3>" ; 
 $a  =  5 ; 
echo  "Should be 6: "  . ++ $a  .  "<br />\n" ; 
echo  "Should be 6: "  .  $a  .  "<br />\n" ; 
 
echo  "<h3>Postdecrement</h3>" ; 
 $a  =  5 ; 
echo  "Should be 5: "  .  $a -- .  "<br />\n" ; 
echo  "Should be 4: "  .  $a  .  "<br />\n" ; 
 
echo  "<h3>Predecrement</h3>" ; 
 $a  =  5 ; 
echo  "Should be 4: "  . -- $a  .  "<br />\n" ; 
echo  "Should be 4: "  .  $a  .  "<br />\n" ; 
 ?>

PHP follows Perl's convention when dealing with arithmetic operations on character variables and not C's. For example, in Perl 'Z'+1 turns into 'AA', while in C 'Z'+1 turns into '[' ( ord('Z') == 90, ord('[') == 91 ). Note that character variables can be incremented but not decremented and even so only plain ASCII characters (a-z and A-Z) are supported.

Example #1 Arithmetic Operations on Character Variables

  <?php 
$i  =  'W' ; 
for ( $n = 0 ;  $n < 6 ;  $n ++) { 
    echo ++ $i  .  "\n" ; 
} 
 ?>

The above example will output:

X
Y
Z
AA
AB
AC

Incrementing or decrementing booleans has no effect.

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