## Incrementing/Decrementing Operators

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

> Note: The increment/decrement operators only affect numbers and strings. Arrays, objects, booleans and resources are not affected. 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 PHP and Perl $a = 'Z'; $a++; turns $a into 'AA', while in C a = 'Z'; a++; turns a into '[' (ASCII value of 'Z' is 90, ASCII value of '[' is 91). Note that character variables can be incremented but not decremented and even so only plain ASCII alphabets and digits (a-z, A-Z and 0-9) are supported. Incrementing/decrementing other character variables has no effect, the original string is unchanged.

Example #1 Arithmetic Operations on Character Variables

`<?php
echo '== Alphabets ==' . PHP_EOL;
$s = 'W';
for ($n=0; $n<6; $n++) {
echo ++$s . PHP_EOL;
}
// Digit characters behave differently
echo '== Digits ==' . PHP_EOL;
$d = 'A8';
for ($n=0; $n<6; $n++) {
echo ++$d . PHP_EOL;
}
$d = 'A08';
for ($n=0; $n<6; $n++) {
echo ++$d . PHP_EOL;
}
?>`

The above example will output:

    == Characters ==
    X
    Y
    Z
    AA
    AB
    AC
    == Digits ==
    A9
    B0
    B1
    B2
    B3
    B4
    A09
    A10
    A11
    A12
    A13
    A14

Incrementing or decrementing booleans has no effect.