## Integers

An int is a number of the set ℤ = {..., -2, -1, 0, 1, 2, ...}.

See also:

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

### 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). 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.

Example #1 Integer literals

`<?php
$a = 1234; // decimal number
$a = 0123; // octal number (equivalent to 83 decimal)
$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 7.4.0 (previously, underscores have not been allowed):

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

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

    octal       : 0[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.

Example #2 Integer overflow on a 32-bit system

`<?php
$large_number = 2147483647;
var_dump($large_number); // int(2147483647)
$large_number = 2147483648;
var_dump($large_number); // float(2147483648)
$million = 1000000;
$large_number = 50000 * $million;
var_dump($large_number); // float(50000000000)
?>`

Example #3 Integer overflow on a 64-bit system

`<?php
$large_number = 9223372036854775807;
var_dump($large_number); // int(9223372036854775807)
$large_number = 9223372036854775808;
var_dump($large_number); // float(9.2233720368548E+18)
$million = 1000000;
$large_number = 50000000000000 * $million;
var_dump($large_number); // float(5.0E+19)
?>`

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.

#### From booleans

`FALSE` will yield `0` (zero), and `TRUE` will yield `1` (one).

#### From floating point numbers

When converting from float to int, the number will be rounded towards zero.

If the float is beyond the boundaries of int (usually `+/- 2.15e+9 = 2^31` on 32-bit platforms and `+/- 9.22e+18 = 2^63` on 64-bit platforms), the result is undefined, since the float doesn't have enough precision to give an exact int result. No warning, not even a notice will be issued when this happens!

> Note:

> NaN and Infinity will always be zero when cast to int.

Warning

Never cast an unknown fraction to int, as this can sometimes lead to unexpected results.

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

See also the warning about float precision.

#### From strings

See String conversion to numbers

#### From NULL

`NULL` is always converted to zero (`0`).

#### From other types

Caution

The behaviour of converting to int is undefined for other types. Do not rely on any observed behaviour, as it can change without notice.