Web Database Applications with PHP and MySQL, 2nd Edition

Integers and Floats

As we discussed in Chapter 2, PHP supports both integer and floating-point numbers. PHP stores integers as a 32-bit signed word, providing a range of integers from -2147483647 to [phone]. PHP automatically converts numbers that overflow out of this range to floats. You can see this behavior by adding one to the largest integer value:

// Largest positive integer (for a 32 bit signed integer)
$variable =  2147483647;

// prints int(2147483647)
var_dump($variable);

$variable++;

// prints float(2147483648)
var_dump($variable);

Floating-point numbers can store a wide range of values, both very large and very small, by storing a mantissa and an exponent. However a floating-point number can't precisely represent all numbers—for example, the fraction 2/3—and some precision can be lost.

Integers can be represented in a decimal, hexadecimal, or octal notation:

$var = 42;        // a positive integer
$var = -186;      // a negative integer
$var = 0654;      // 428 expressed as an octal number
$var = 0xf7;      // 247 expressed as a hexadecimal number

Floating-point numbers can represented in a decimal or exponential notation:

$var = 42.0;      // a positive float
$var = -186.123;  // a negative float
$var = 1.2e65;    // a very big number
$var = 10e-75;    // a very small number

Apart from the basic operators +, -, /, *, and %, PHP provides the usual array of mathematical library functions. In this section, we present some of the library functions that are used with integer and float numbers.

Absolute Value ...