PHP Numbers

In this chapter we will look in depth into Integers, Floats, and Number Strings.

PHP Numbers

There are three main numeric types in PHP:

• Integer
• Float
• Number Strings

In addition, PHP has two more data types used for numbers:

• Infinity
• NaN

Variables of numeric types are created when you assign a value to them:

$a = 5;
$b = 5.34;
$c = "25";

To verify the type of any object in PHP, use the var_dump() function:

var_dump($a);
var_dump($b);
var_dump($c);

PHP Integers

The PHP is_int() function is used to check if the type of a variable is integer.

An integer is a number without any decimal part: 2, 256, -256, 10358, -179567 are all integers.

$x = 5985;
var_dump(is_int($x));

$x = 59.85;
var_dump(is_int($x));

An integer data type is a non-decimal number between -2147483648 and 2147483647 in 32 bit systems, and between -9223372036854775808 and 9223372036854775807 in 64 bit systems. A value greater (or lower) than this, will be stored as float, because it exceeds the limit of an integer.

Note: Another important thing to know is that even if 4 * 2.5 is 10, the result is stored as float, because one of the operands is a float (2.5).

Here are some rules for integers:

• An integer must have at least one digit
• An integer must NOT have a decimal point
• An integer can be either positive or negative
• Integers can be specified in three formats: decimal (base 10), hexadecimal (base 16 - prefixed with 0x), octal (base 8 - prefixed with 0) or binary (base 2 - prefixed with 0b)

PHP has the following predefined constants for integers:

• PHP_INT_MAX - The largest integer supported
• PHP_INT_MIN - The smallest integer supported
• PHP_INT_SIZE -  The size of an integer in bytes

PHP Floats

The PHP is_float() function is used to check if the type of a variable is float.

A float is a number with a decimal point or a number in exponential form: 2.0, 256.4, 10.358, 7.64E+5, 5.56E-5 are all floats.

$x = 10.365;
var_dump(is_float($x));

The float data type can commonly store a value up to 1.7976931348623E+308 (platform dependent), and have a maximum precision of 14 digits.

PHP has the following predefined constants for floats (from PHP 7.2):

• PHP_FLOAT_MAX - The largest representable floating point number
• PHP_FLOAT_MIN - The smallest representable positive floating point number
• PHP_FLOAT_DIG - The number of decimal digits that can be rounded into a float and back without precision loss
• PHP_FLOAT_EPSILON - The smallest representable positive number x, so that x + 1.0 != 1.0

PHP Infinity

The PHP is_finite() function checks whether a value is finite or not.

A value is finite if it is within the allowed range for a PHP float on this platform.

The PHP is_infinite() function checks whether a value is infinite or not.

The value is infinite if it is outside the allowed range for a PHP float on this platform.

$x = 1.9e411;
var_dump(is_infinite($x));

PHP NaN

NaN stands for Not a Number.

NaN is used for impossible mathematical operations.

The PHP is_nan() function is used to check if a value is not a number.

$x = acos(8);
var_dump($x);

PHP Numerical Strings

The PHP is_numeric() function is used to check whether a variable is a number or a numeric string.

This function returns true if the variable is a number or a numeric string, false otherwise.

$x = 5985;
var_dump(is_numeric($x));

$x = "5985";
var_dump(is_numeric($x));
$x = "59.85" + 100;
var_dump(is_numeric($x));

$x = "Hello";
var_dump(is_numeric($x));

PHP Casting Strings and Floats to Integers

Sometimes you need to cast a numerical value into another data type.

The (int), (integer), and intval() functions are often used to convert a value to an integer.

// Cast float to int
$x = 23465.768;
$int_cast = (int)$x;
echo $int_cast;

echo "<br>";

// Cast string to int
$x = "23465.768";
$int_cast = (int)$x;
echo $int_cast;

Learn more about casting in the PHP Casting chapter.