What is an increment and a decrement?

Increment — increasing the value of a variable by one.

Decrement — decreasing the value of a variable by one.

Increment and decrement operators in PHP:

• ++$var (prefix increment): first increases $var, then returns the new value.
• $var++ (postfix increment): first returns the current value of $var, then increases it.
• --$var (prefix decrement): first decreases $var, then returns the new value.
• $var-- (postfix decrement): first returns the current value of $var, then decreases it.

Examples of usage:

<?php
$a = 5;
echo ++$a; // Outputs 6, $a is now 6

$b = 5;
echo $b++; // Outputs 5, $b is now 6

$c = 5;
echo --$c; // Outputs 4, $c is now 4

$d = 5;
echo $d--; // Outputs 5, $d is now 4
?>