2.3 PHP Numbers

PHP Integers

• An integer is a number without any decimal part.
• 2, 256, -256, 10358, -179567 are all integers. While 7.56, 10.0, 150.67 are floats.
• So, an integer data type is a non-decimal number between -2147483648 and 2147483647. A value greater (or lower) than this, will be stored as float, because it exceeds the limit of an integer.
• 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 (10-based), hexadecimal (16-based - prefixed with 0x) or octal (8-based - prefixed with 0)
• PHP has the following functions to check if the type of a variable is integer:
  • is_int()
  • is_integer() - alias of is_int()
  • is_long() - alias of is_int()

Example 1: PHP Numbers - Integers is_int()

Check if the type of a variable is integer:

<?php
$x = 5985;
var_dump(is_int($x));

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

PHP Floats

• 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.
• 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 functions to check if the type of a variable is float:
  • is_float()
  • is_double() - alias of is_float()

Example 2: PHP Numbers - Floats is_float()

Check if the type of a variable is float:

<?php
$x = 10.365;
var_dump(is_float($x));
?>

PHP Infinity

• A numeric value that is larger than PHP_FLOAT_MAX is considered infinite.
• PHP has the following functions to check if a numeric value is finite or infinite:
  • is_finite()
  • is_infinite()
• However, the PHP var_dump() function returns the data type and value:

Example 3: PHP Numbers - Check if a numeric value is finite

Check if a numeric value is finite or infinite:

<?php
$x = 1.9e411;
var_dump($x);
?>

PHP NaN

• NaN stands for Not a Number.
• NaN is used for impossible mathematical operations.
• PHP has the following functions to check if a value is not a number:
  • is_nan()
• However, the PHP var_dump() function returns the data type and value:

Example 4: PHP Numbers - Invalid calculation will return a NaN value:

Invalid calculation will return a NaN value:

<?php
$x = acos(8);
var_dump($x);
?>

PHP Numerical Strings

The PHP is_numeric() function can be used to find whether a variable is numeric. The function returns true if the variable is a number or a numeric string, false otherwise.

Example 5: PHP Numbers - Check if the variable is numeric

Check if the variable is numeric:

<?php
$x = 5985;
var_dump(is_numeric($x));

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

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

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

Note: From PHP 7.0: The is_numeric() function will return FALSE for numeric strings in hexadecimal form (e.g. 0xf4c3b00c), as they are no longer considered as numeric strings.

PHP Casting Strings and Floats to Integers

• Sometimes you need to cast a numerical value into another data type.
• The (int), (integer), or intval() function are often used to convert a value to an integer.

Example 6: PHP Numbers - Cast float to int

Cast float and string to integer:

<?php
// 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;
?>