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PHP supports C-style pre- and post-increment and decrement operators.
Note: The increment/decrement operators only affect numbers and strings. Arrays, objects and resources are not affected. Decrementing
NULLvalues has no effect too, but incrementing them results in 1.
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
A14Incrementing or decrementing booleans has no effect.
← Execution Operators
Logical Operators →
? 1997–2017 The PHP Documentation GroupLicensed under the Creative Commons Attribution License v3.0 or later.
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