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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.

Table 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:

`<?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.

Example 15-4. 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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