PHP Increment & Decrement

Increment and decrement are shortcuts for adding one or taking one away, like clicking a tally counter. It matters whether PHP counts before or after it gives you the number.

In this page:

Post-Increment Operator
Pre-Increment Operator
Post-Decrement Operator
Pre-Decrement Operator
Incrementing Characters

Syntax

php

$x++;   // post-increment: use value, then add 1
++$x;   // pre-increment: add 1, then use value
$x--;   // post-decrement
--$x;   // pre-decrement

Post-Increment Operator

$x++ (post-increment) reads out $x's current value first, and only *after* that read does PHP add 1 to the variable.

If you use the expression's result directly, you get the value from before the increment — the update happens, just invisibly to that particular expression.

Example: Post-Increment Operator

php

<?php
// Declare `$x`, set to `5`
$x = 5;
// Print `$x++` to the output
echo $x++;
// Print "\n" to the output
echo "\n";
// Print `$x` to the output
echo $x;
?>

Pre-Increment Operator

++$x (pre-increment) adds 1 to the variable first, then returns the already-updated value.

Whether you use pre- or post-increment only matters when you use the expression's *result* somewhere else in the same line — as a standalone statement, $x++ and ++$x behave identically.

Example: Pre-Increment Operator

php

<?php
// Declare `$x`, set to `5`
$x = 5;
// Print `++$x` to the output
echo ++$x;
// Print "\n" to the output
echo "\n";
// Print `$x` to the output
echo $x;
?>

Post-Decrement Operator

$x-- (post-decrement) mirrors post-increment: it returns the current value, then subtracts 1 afterward. It's the natural choice for a countdown loop where you want to act on the value *before* it decreases on that iteration.

Example: Post-Decrement Operator

php

<?php
// Declare `$x`, set to `5`
$x = 5;
// Print `$x--` to the output
echo $x--;
// Print "\n" to the output
echo "\n";
// Print `$x` to the output
echo $x;
?>

Pre-Decrement Operator

--$x (pre-decrement) subtracts 1 first and returns the new, already-lower value.

As with pre-increment, the difference from the post- version only shows up when the expression's return value is actually consumed rather than the statement standing alone.

Example: Pre-Decrement Operator

php

<?php
// Declare `$x`, set to `5`
$x = 5;
// Print `--$x` to the output
echo --$x;
// Print "\n" to the output
echo "\n";
// Print `$x` to the output
echo $x;
?>

Incrementing Characters

PHP has an unusual extra ability: incrementing a string containing letters advances it alphabetically — $letter = a; $letter++; produces b, and incrementing z rolls over to aa, the same way a car odometer carries over a digit.

Example: Incrementing Characters

php

<?php
// Declare `$letter`, set to 'a'
$letter = 'a';
$letter++;
// Print `$letter . "\n"` to the output
echo $letter . "\n";

// Declare `$letter`, set to 'z'
$letter = 'z';
$letter++;
// Print `$letter` to the output
echo $letter;
?>

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