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## Integers

An integer 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

Integer s can be specified in decimal (base 10), hexadecimal (base 16), or octal (base 8) notation, optionally preceded by a sign (- or +).

To use octal notation, precede the number with a 0 (zero). To use hexadecimal notation precede the number with 0x.

Beispiel #1 Integer literals

`<?php
$a = 1234; // decimal number
$a = -123; // a negative number
$a = 0123; // octal number (equivalent to 83 decimal)
$a = 0x1A; // hexadecimal number (equivalent to 26 decimal)
?>`

Formally, the structure for integer literals is:

    decimal     : [1-9][0-9]*
                | 0

    hexadecimal : 0[xX][0-9a-fA-F]+

    octal       : 0[0-7]+

    integer     : [+-]?decimal
                | [+-]?hexadecimal
                | [+-]?octal

The size of an integer is platform-dependent, although a maximum value of about two billion is the usual value (that's 32 bits signed). PHP does not support unsigned integer s. Integer size can be determined using the constant `PHP_INT_SIZE`, and maximum value using the constant `PHP_INT_MAX` since PHP 4.4.0 and PHP 5.0.5.

Warnung

If an invalid digit is given in an octal integer (i.e. 8 or 9), the rest of the number is ignored.

Beispiel #2 Octal weirdness

`<?php
var_dump(01090); // 010 octal = 8 decimal
?>`

### Integer overflow

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

`<?php
$large_number = 2147483647;
var_dump($large_number);
// output: int(2147483647)
$large_number = 2147483648;
var_dump($large_number);
// output: float(2147483648)
// it's true also for hexadecimal specified integers between 2^31 and 2^32-1:
var_dump( 0xffffffff );
// output: float(4294967295)
// this doesn't go for hexadecimal specified integers above 2^32-1:
var_dump( 0x100000000 );
// output: int(2147483647)
$million = 1000000;
$large_number = 50000 * $million;
var_dump($large_number);
// output: float(50000000000)
?>`
Warnung

Unfortunately, there was a bug in PHP which caused this to not always work correctly when negative numbers were involved. For example, the result of -50000 * $million is -429496728. However, when both operands were positive, there was no problem.

This was fixed in PHP 4.1.0.

There is no integer division operator in PHP. 1/2 yields the float 0.5. The value can be casted to an integer to round it downwards, 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 integer , 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 integer argument. A value can also be converted to integer with the intval() function.

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 integer , the number will be rounded towards zero.

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

Warnung

Never cast an unknown fraction to integer , 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 other types

Achtung

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

Booleans
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PHP Manual