PHP Arithmetic Operators

PHP arithmetic Operators are used to perform mathematical calculations.

Increment and Decrement operators act on numeric values.

Example:

<?php
    $var = 1;       // Assign the integer 1 to $var
    echo $var++;    // Print 1, $var is now equal to 2
    echo ++$var;    // Print 3, $var is now equal to 3
    echo --$var;    // Print 2, $var is now equal to 2
    echo $var--;    // Print 2, $var is now equal to 1
?>

Referencing Variables

By default, assignment operators work by value—that is, they copy the value of an expression on to another. If the right-hand operand happens to be a variable, only its value is copied, so that any subsequent change to the left-hand operator is not reflected in the right-hand one.

Example:

<?php
    $a = 5;
    $b = $a;
    $b = 10;
    echo $a; // Print 5
?>

Naturally, you expect this to be the case, but there are circumstances in which you may want an assignment to take place by reference so that the left-hand operand becomes "connected" with the right-hand one:

Example:

<?php
    $a = 5;
    $b = &$a; // Reference
    $b = 10;
    echo $a; // Print 10 
?>