Enteros

Un entero o integer es un número del conjunto ℤ = {..., -2, -1, 0, 1, 2, ...}.

Consulte tambien:

Sintaxis

Los integer pueden ser especificados mediante notación decimal (base 10), hexadecimal (base 16), octal (base 8) o binaria (base 2), opcionalmente precedidos por un signo (- o +).

Los literales integer binarios están disponibles desde PHP 5.4.0.

Para usar la notación octal, se antepone al número un 0 (cero). Para usar la notación hexadecimal, se antepone al número un 0x. Para usar la notación binaria, se antepone al número un 0b.

Ejemplo #1 Enteros literales

<?php
$a 
1234// número decimal
$a = -123// un número negativo
$a 0123// número octal (equivalente a 83 decimal)
$a 0x1A// número hexadecimal (equivalente a 26 decimal)
$a 0b11111111// número binario (equivalente al 255 decimal)
?>

Formalmente, la estructura de integer literales es:

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

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

octal       : 0[0-7]+

binario     : 0b[01]+

entero      : [+-]?decimal
            | [+-]?hexadecimal
            | [+-]?octal
            | [+-]?binary

El tamaño de un integer depende de la plataforma, aunque un valor máximo de aproximadamente dos mil millones es el valor usual (para 32 bits con signo). Las plataformas de 64-bits normalmente tienen un valor máximo de aproximadamente 9E18. PHP no admite integers sin signo. El tamaño de un integer puede ser determinado mediante la constante PHP_INT_SIZE y el valor máximo mediante la constante PHP_INT_MAX desde PHP 4.4.0 y PHP 5.0.5.

Advertencia

Si en un integer octal se da un dígito incorrecto (por ejemplo 8 o 9), el resto del número se ignora.

Ejemplo #2 Octal raros

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

Desbordamiento de enteros

Si PHP encuentra un número fuera de los límites de un integer, se interpretará como un float en su lugar. Tambien, una operación cuyo resultado es un número fuera de los límites de un integer devolverá en su lugar un float.

Ejemplo #3 Desbordamiento de enteros en sistemas 32-bits

<?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)
?>

Ejemplo #4 Desbordamiento de enteros en sistemas 64-bits

<?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)
?>

No existe operador de división de integer en PHP. 1/2produce el float 0.5. El valor puede ser forzado a ser un integer redondeando por defecto, o mediante la función round() que permite un mayor control sobre el redondeo.

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

Conversión a enteros

Para convertir explicitamente un valor a integer, se puede emplear tanto (int) como (integer). Sin embargo, la mayoría de las veces la conversión no es necesaria, ya que un valor es convertido de forma automática cuando un operador, función o estructura de control necesite un argumento del tipo integer. Un valor tambien puede ser convertido a integer mediante la función intval().

Consulte también la manipulación de tipos.

Desde booleanos

FALSE produce 0 (cero), y TRUE produce 1 (uno).

Desde números de punto flotante

Cuando se convierte de un float a un integer, el número será redondeado hacia cero.

Si el float esta por debajo de los límites de un integer (normalmente +/- 2.15e+9 = 2^31 en plataformas de 32 bits y +/- 9.22e+18 = 2^63 en plataformas de 64 bits), el resultado es indefinido, debido a que float no tiene la precisión suficiente para ofrecer el resultado como un integer exacto. No se mostrará ninguna advertencia, ni siquiera un aviso cuando esto ocurre!

Advertencia

Nunca se debe convertir una fracción desconocida a un integer, ya que a veces puede producir resultados inesperados.

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

Consulte tambien aviso sobre la precisión de float

Desde cadenas

Consulte Conversión de cadenas a números

Desde otros tipos

Precaución

El comportamiento de la conversion de integer a otros tipos es indefinido. No espere que exista un comportamiento esperado, ya que puede cambiar sin previo aviso.

add a note add a note

User Contributed Notes 22 notes

up
23
Paul
6 years ago
"always round it downwards"

It seems to truncate, or round toward zero, rather than downward. If the float is negative, it is rounded up.
up
11
rustamabd@gmail-you-know-what
7 years ago
Be careful with using the modulo operation on big numbers, it will cast a float argument to an int and may return wrong results. For example:
<?php
    $i
= 6887129852;
    echo
"i=$i\n";
    echo
"i%36=".($i%36)."\n";
    echo
"alternative i%36=".($i-floor($i/36)*36)."\n";
?>
Will output:
i=6.88713E+009
i%36=-24
alternative i%36=20
up
1
Alex
5 months ago
"The behaviour of converting to integer is undefined for other types. Do not rely on any observed behaviour, as it can change without notice."

actually i use type casting to output Boolean like this:

<?php
echo (int)(function_exists('imagecreatetruecolor'));
?>

so i see 0 or 1 in output
up
6
d_n at NOSPAM dot Loryx dot com
6 years ago
Here are some tricks to convert from a "dotted" IP address to a LONG int, and backwards. This is very useful because accessing an IP addy in a database table is very much faster if it's stored as a BIGINT rather than in characters.

IP to BIGINT:
<?php
  $ipArr   
= explode('.',$_SERVER['REMOTE_ADDR']);
 
$ip       = $ipArr[0] * 0x1000000
           
+ $ipArr[1] * 0x10000
           
+ $ipArr[2] * 0x100
           
+ $ipArr[3]
            ;
?>

IP as BIGINT read from db back to dotted form:

Keep in mind, PHP integer operators are INTEGER -- not long. Also, since there is no integer divide in PHP, we save a couple of S-L-O-W floor (<division>)'s by doing bitshifts. We must use floor(/) for $ipArr[0] because though $ipVal is stored as a long value, $ipVal >> 24 will operate on a truncated, integer value of $ipVal! $ipVint is, however, a nice integer, so
we can enjoy the bitshifts.

<?php
        $ipVal
= $row['client_IP'];
       
$ipArr = array(0 =>
                   
floor$ipVal               / 0x1000000) );
       
$ipVint   = $ipVal-($ipArr[0]*0x1000000); // for clarity
       
$ipArr[1] = ($ipVint & 0xFF0000)  >> 16;
       
$ipArr[2] = ($ipVint & 0xFF00  )  >> 8;
       
$ipArr[3] =  $ipVint & 0xFF;
       
$ipDotted = implode('.', $ipArr);
?>
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6
Anonymous
10 years ago
Sometimes you need to parse an unsigned
32 bit integer. Here's a function I 've used:
                                                                               
    function parse_unsigned_int($string) {
        $x = (float)$string;
        if ($x > (float)2147483647)
            $x -= (float)"4294967296";
        return (int)$x;
    }
up
4
Anonymous
7 years ago
To force the correct usage of 32-bit unsigned integer in some functions, just add '+0'  just before processing them.

for example
echo(dechex("2724838310"));
will print '7FFFFFFF'
but it should print 'A269BBA6'

When adding '+0' php will handle the 32bit unsigned integer
correctly
echo(dechex("2724838310"+0));
will print 'A269BBA6'
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3
Hamza Burak Ylmaz
5 years ago
<?php
//This is a simple function to return number of digits of an integer.

//function declaration
function count_digit($number)
{
   
$digit = 0;
    do
    {
       
$number /= 10;      //$number = $number / 10;
       
$number = intval($number);
       
$digit++;   
    }while(
$number!=0);
    return
$digit;
}

//function call
$num = 12312;
$number_of_digits = count_digit($num); //this is call :)
echo $number_of_digits;
//prints 5
?>
up
1
darkshire
6 years ago
d_n at NOSPAM dot Loryx dot com
13-Aug-2007 05:33
Here are some tricks to convert from a "dotted" IP address to a LONG int, and backwards. This is very useful because accessing an IP addy in a database table is very much faster if it's stored as a BIGINT rather than in characters.

IP to BIGINT:
<?php
  $ipArr   
= explode('.',$_SERVER['REMOTE_ADDR']);
 
$ip       = $ipArr[0] * 0x1000000
           
+ $ipArr[1] * 0x10000
           
+ $ipArr[2] * 0x100
           
+ $ipArr[3]
            ;
?>

This can be written in a bit more efficient way:
<?php
  $ipArr   
= explode('.',$_SERVER['REMOTE_ADDR']);
 
$ip       = $ipArr[0]<<24
           
+ $ipArr[1]<<16
           
+ $ipArr[2] <<8
           
+ $ipArr[3]
            ;
?>

shift is more cheaper.
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1
popefelix at gmail dot com
7 years ago
Be careful when using integer conversion to test something to see if it evaluates to a positive integer or not.  You might get unexpected behaviour.

To wit:
<?php
error_reporting
(E_ALL);
require_once
'Date.php';

$date = new Date();
print
"\$date is an instance of " . get_class($date) . "\n";
$date += 0;
print
"\$date is now $date\n";
var_dump($date);

$foo = new foo();
print
"\$foo is an instance of " . get_class($foo) . "\n";
$foo += 0;
print
"\$foo is now $foo\n";
var_dump($foo);

class
foo {
    var
$bar = 0;
    var
$baz = "la lal la";
    var
$bak;

    function
foo() {
       
$bak = 3.14159;
    }
}
?>

After the integer conversion, you might expect both $foo and $date to evaluate to 0.  However, this is not the case:

$date is an instance of Date

Notice: Object of class Date could not be converted to int in /home/kpeters/work/sketches/ObjectSketch.php on line 7
$date is now 1
int(1)
$foo is an instance of foo

Notice: Object of class foo could not be converted to int in /home/kpeters/work/sketches/ObjectSketch.php on line 13
$foo is now 1
int(1)

This is because the objects are first converted to boolean before being converted to int.
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0
pere dot cil at wanadoo dot fr
3 years ago
Please also note that the maximum stored in the integer depends on the platform / compilation; on windows xp 32 bits, the following value:

0x5468792130ABCDEF

echoes to:

6.0822444802213E+18 (cast to float)

On a fully 64 bits system, it echoes to:

6082244480221302255
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-2
php at richardneill dot org
1 year ago
A leading zero in a numeric literal means "this is octal". But don't be confused: a leading zero in a string does not. Thus:
$x = 0123;          // 83
$y = "0123" + 0     // 123
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-2
wbcarts at juno dot com
5 years ago
PHP offers a slew of built-in functions and automatic type-casting routines which can get pretty complicated. But most of the time, you still have to take matters into your own hands and allow PHP to do its thing. In that case, and something that has NOT been mentioned, is how to construct your code. To keep things simple, I divide all my scripts in half. The top half gives my scripts the "capability" they need, and the lower half is the actual code to be "run" or "executed".

<?php
/*
* build the program's capability - define variables and functions...
*/
$item_label = '';        // type string
$item_price = 0.0;       // type float
$item_qty = 1;           // type integer
$item_total = 0.0;       // type float - to set use calculate()

function calculate(){
  global
$item_price, $item_qty, $item_total;
 
$item_price = number_format($item_price, 2);
 
$item_total = number_format(($item_price * $item_qty), 2);
}

function
itemToString() {
  global
$item_label, $item_price, $item_qty, $item_total;
  return
"$item_label [price=\$$item_price, qty=$item_qty, total=\$$item_total]";
}

/*
* run the program - set data, call methods...
*/
$item_label = "Coffee";
$item_price = 3.89;
$item_qty = 2;
calculate();           // set $item_total
echo itemToString();   // -> Coffee [price=$3.89, qty=2, total=$7.78]

$item_label = "Chicken";
$item_price = .80;     // per lb.
$item_qty = 3.5;       // lbs.
calculate();           // set $item_total
echo itemToString();   // -> Chicken [price=$0.80, qty=3.5, total=$2.80]
?>
Note: All type-casting is done by PHP's built-in number_format() method. This allows our program to enter any number (float or int) on item price or quantity in the runtime part of our script. Also, if we explicitly cast values to integer in the capability part of our script, then we start getting results that may not be desirable for this program. For example, if in the calculate method we cast item_qty to integer, then we can no longer sell chicken by the pound!
up
-2
Jacek
7 years ago
On 64 bits machines max integer value is 0x7fffffffffffffff (9 223 372 036 854 775 807).
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-3
rickard_cedergren at yahoo dot com
9 years ago
When doing large subtractions on 32 bit unsigned integers the result sometimes end up negative. My example script converts a IPv4 address represented as a 32 bit unsigned integer to a dotted quad (similar to ip2long()), and adds a "fix" to the operation.

   /**************************
    * int_oct($ip)
    * Convert INTeger rep of IP to octal (dotted quad)
    */
   function int_oct($ip) {

      /* Set variable to float */
      settype($ip, float);

      /* FIX for silly PHP integer syndrome */
      $fix = 0;
      if($ip > 2147483647) $fix = 16777216;

      if(is_numeric($ip)) {
         return(sprintf("%u.%u.%u.%u",
                $ip / 16777216,
                (($ip % 16777216) + $fix) / 65536,
                (($ip % 65536) + $fix / 256) / 256,
                ($ip % 256) + $fix / 256 / 256
                )
     );
      }
      else {
         return('');
      }
   }
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-4
iletras at yahoo dot com
3 years ago
//This is a (simpler ?) function to return number of digits of an integer.

//function declaration
function count_digit($number) {
  return  strlen((string) $number);
}

//function call
$num = 12312;
$number_of_digits = count_digit($num); //this is call :)
echo $number_of_digits;
//prints 5
up
-4
jmw254 at cornell dot edu
7 years ago
Try this one instead:

function iplongtostring($ip)
{
    $ip=floatval($ip); // otherwise it is capped at 127.255.255.255

    $a=($ip>>24)&255;
    $b=($ip>>16)&255;
    $c=($ip>>8)&255;
    $d=$ip&255;

    return "$a.$b.$c.$d";
}
up
-5
eric
6 years ago
In response to the comment by me at troyswanson dot net:

-2147483648 falls into the range of 32 bit signed integers yet php treats it as a float.  However, -2147483647-1 is treated as an integer.

The following code demonstrates:
<?php
    var_dump
(-2147483648); //float(-2147483648)
   
var_dump(-2147483647 - 1); //int(-2147483648)
?>

This is probably very similar to the MS C bug which also treats -2147483648 as an UNSIGNED because it thinks it's out of the range of a signed int.

The problem is that the parser does not view "-x" as a single token, but rather as two, "-" and "x".  Since "x" is out of the range of an INT, it is promoted to float, even though in this unique case, "-x" is in the range of an int.

The best cure is probably to replace "-2147483648" with "0x80000000", as that is the hexadecimal equivalent of the same number.

Hope that helps explain what's going on

Peace

- Eric / fez
up
-7
autotelic at NOOOOSPAM dot hotmail dot com
6 years ago
A note about converting IP addresses for storage in database.  For MySQL, this is unnecessary as it has built in support via the INET functions.  Also, there is no need to use BIGINT.  UNSIGNED INT is, at 4 bytes, the perfect size for holding an IP (column must be defined as UNSIGNED).  This can basically halve the storage size, as BIGINT is an 8 byte data type.

INET_ATON() converts a dotted IP string to INT:
INSERT table(ip) VALUES(INET_ATON('127.0.0.1'));

INET_NTOA() converts an INT to dotted IP string:
SELECT INET_NTOA(ip) FROM table
returns '127.0.0.1'

Details:
http://dev.mysql.com/doc/refman/5.1/en/miscellaneous-functions.html
up
-7
winterheat
6 years ago
PHP_INT_SIZE seems to be 8 when it is 64 bit integers... so 8 means the number of bytes, or number of 8-bits.
up
-8
sean dot gilbertson at gmail dot com
5 years ago
You can make a signed, negative integer an unsigned integer (in string form) by doing the following:

<?php
$unsigned
= sprintf('%u', -5);

echo
$unsigned; // prints 4294967291
?>
up
-9
php at keith tyler dot com
3 years ago
If you need to convert a numeric string (or more to the point, an object that represents a numeric value) that is greater then PHP_INT_MAX, and you don't have GMP or BCMath installed, you can cast to float.

For example, when using SimpleXMLElement, you sometimes have to cast the extracted values, such as xml attributes, because they are returned as SimpleXMLElements and not their values' native types. While print() has no trouble with converting them, other functions, such as max(), might not.

But if you cast such a value with (int), and it is over PHP_INT_MAX, you will just get PHP_INT_MAX (and vice versa for negative numbers).

The Q&D no-muss solution is to cast to (float) instead.
up
-10
Richard
3 years ago
Integer arithmetic in PHP is more accurate than one might think. On a 32-bit system, the largest value that can be held in an INT is  2147483647.
However, a FLOAT can accurately hold integer values up to 10000000000000.
(this is because the significand precision of a double is 53-bits).
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