Incrementing/Decrementing Operators\
PHP supports C-style pre- and post-increment and decrement
operators.
Table 10-5. 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
10-1. Arithmetic Operations on Character Variables
<?php
$i = 'W';
for($n=0; $n<6; $n++)
echo ++$i . "\n";
/*
Produces the output similar to the following:
X
Y
Z
AA
AB
AC
*/
?>
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