Incrementing/Decrementing Operators

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

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

???? 15-6. 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:

echo " Postincrement "; $a = 5; echo "Should be 5: " . $a++ . " \n"; echo "Should be 6: " . $a . " \n"; echo " Preincrement "; $a = 5; echo "Should be 6: " . ++$a . " \n"; echo "Should be 6: " . $a . " \n"; echo " Postdecrement "; $a = 5; echo "Should be 5: " . $a-- . " \n"; echo "Should be 4: " . $a . " \n"; echo " Predecrement "; $a = 5; echo "Should be 4: " . --$a . " \n"; echo "Should be 4: " . $a . " \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.

????? 15-4. Arithmetic Operations on Character Variables $i = 'W'; for ($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.