PHP Increment and Decrement Operators: ++ and --

Adding or subtracting 1 is so common that PHP has a shortcut.

Operator	Meaning
`$i++`	Add 1 to `$i`
`$i--`	Subtract 1 from `$i`

index.php

PHP

<?php
$count = 5;

$count++;
echo $count . "\n";

$count--;
$count--;
echo $count;

Output

OUTPUT

1
2

6
4

Prefix and postfix

The operator can come before or after the variable, and that changes what the expression returns.

Postfix ($i++): returns the old value, then adds 1.
Prefix (++$i): adds 1 first, then returns the new value.

index.php

PHP

<?php
$a = 5;
echo $a++ . "\n";  // prints 5, then $a becomes 6
echo $a . "\n";

$b = 5;
echo ++$b . "\n";  // $b becomes 6, then prints 6
echo $b;

Output

OUTPUT

When you use ++ as its own statement, as in $i++;, both forms do exactly the same thing.

Where you see it

Counting inside a loop:

index.php

PHP

<?php
for ($i = 1; $i <= 3; $i++) {
    echo "Round $i\n";
}

Output

OUTPUT

1
2
3

Round 1
Round 2
Round 3

Counting how many times something happens:

index.php

PHP

<?php
$words = ["php", "sql", "php", "css", "php"];
$phpCount = 0;

foreach ($words as $word) {
    if ($word === "php") {
        $phpCount++;
    }
}

echo $phpCount;

Output

OUTPUT

lightbulb

Keep it on its own line

$total = $i++ + ++$i; is legal and hard to read. Use ++ and -- as separate statements so nobody has to think about the order.