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Expressions, Operators, and Variable Assignment

We've already described simple examples of assignment, in which a variable is assigned the value of an expression using an equals sign. Most numeric assignments and expressions that work in other high-level languages also work in PHP. Here are some examples:

// Assign a value to a variable
$var = 1;

// Sum integers to produce an integer
$var = 4 + 7;

// Subtraction, multiplication, and division
// that might have a result that is a float or
// an integer, depending on the initial value of $var
$var = (($var - 5) * 2) / 3;

// These all add 1 to $var
$var = $var + 1;
$var += 1;
$var++;

// And these all subtract 1 from $var
$var = $var - 1;
$var -= 1;
$var--;

// Double a value
$var = $var * 2;
$var *= 2;

// Halve a value
$var = $var / 2;
$var /= 2;

// These work with float types too
$var = 123.45 * 28.2;

There are many mathematical functions available in the math library of PHP for more complex tasks. We introduce some of these in Section 2.9.

String assignments and expressions are similar:

// Assign a string value to a variable
$var = "test string";

// Concatenate two strings together
// to produce "test string"
$var = "test" . " string";

// Add a string to the end of another
// to produce "test string"
$var = "test";
$var = $var . " string";

// Here is a shortcut to add a string to
// the end of another
$var .= " test";

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