See Also

• Floating point numbers
• Arbitrary precision / BCMath
• Arbitrary length integer / GMP

Syntax

Ints can be specified in decimal (base 10), hexadecimal (base 16), octal (base 8) or binary (base 2) notation. The negation operator can be used to denote a negative int.

To use octal notation, precede the number with a 0 (zero). As of PHP 8.1.0, octal notation can also be preceded with 0o or 0O. To use hexadecimal notation precede the number with 0x. To use binary notation precede the number with 0b.

As of PHP 7.4.0, integer literals may contain underscores (_) between digits, for better readability of literals. These underscores are removed by PHP's scanner.

<?php
$a = 1234; // decimal number
$a = 0123; // octal number (equivalent to 83 decimal)
$a = 0o123; // octal number (as of PHP 8.1.0)
$a = 0x1A; // hexadecimal number (equivalent to 26 decimal)
$a = 0b11111111; // binary number (equivalent to 255 decimal)
$a = 1_234_567; // decimal number (as of PHP 7.4.0)
?>

Formally, the structure for int literals is as of PHP 8.1.0 (previously, the 0o or 0O octal prefixes were not allowed, and prior to PHP 7.4.0 the underscores were not allowed):

decimal     : [1-9][0-9]*(_[0-9]+)*
            | 0

hexadecimal : 0[xX][0-9a-fA-F]+(_[0-9a-fA-F]+)*

octal       : 0[oO]?[0-7]+(_[0-7]+)*

binary      : 0[bB][01]+(_[01]+)*

integer     : decimal
            | hexadecimal
            | octal
            | binary

The size of an int is platform-dependent, although a maximum value of about two billion is the usual value (that's 32 bits signed). 64-bit platforms usually have a maximum value of about 9E18. PHP does not support unsigned ints. int size can be determined using the constant PHP_INT_SIZE, maximum value using the constant PHP_INT_MAX, and minimum value using the constant PHP_INT_MIN.

Integer overflow

If PHP encounters a number beyond the bounds of the int type, it will be interpreted as a float instead. Also, an operation which results in a number beyond the bounds of the int type will return a float instead.

<?php
$large_number = 50000000000000000000;
var_dump($large_number);         // float(5.0E+19)

var_dump(PHP_INT_MAX + 1);       // 32-bit system: float(2147483648)
                                 // 64-bit system: float(9.2233720368548E+18)
?>

Integer division

There is no int division operator in PHP, to achieve this use the intdiv function. 1/2 yields the float 0.5. The value can be cast to an int to round it towards zero, or the round function provides finer control over rounding.

<?php
var_dump(25/7);         // float(3.5714285714286)
var_dump((int) (25/7)); // int(3)
var_dump(round(25/7));  // float(4)
?>

Converting to integer

To explicitly convert a value to int, use either the (int) or (integer) casts. However, in most cases the cast is not needed, since a value will be automatically converted if an operator, function or control structure requires an int argument. A value can also be converted to int with the intval function.

If a resource is converted to an int, then the result will be the unique resource number assigned to the resource by PHP at runtime.

See also Type Juggling.

<?php

function foo($value): int {
  return $value; 
}

var_dump(foo(8.1)); // "Deprecated: Implicit conversion from float 8.1 to int loses precision" as of PHP 8.1.0
var_dump(foo(8.1)); // 8 prior to PHP 8.1.0
var_dump(foo(8.0)); // 8 in both cases

var_dump((int) 8.1); // 8 in both cases
var_dump(intval(8.1)); // 8 in both cases
?>

<?php
echo (int) ( (0.1+0.7) * 10 ); // echoes 7!
?>