Booleanos
be careful relying on PHP's data type handling. I have a class that handles database calls and in there a function to handle types and formatting them for insertion.
<?php
case constants::int:
$returnString = ($valueString >= 0) ? $valueString : "null";
break;
?>
Will evaluate to false if a user enters "0" since PHP thinks that the 0 is a Boolean. The following code fixes it:
<?php
case constants::int:
$returnString = ((int)$valueString >= 0) ? (int)$valueString : "null";
break;
?>
Inteiros
Um inteiro é um número do conjunto Z = {..., -2, -1, 0, 1, 2, ...}.
Veja também: Inteiros de tamanho arbitrário / GMP, Números de ponto flutuante e Precisão arbitrária / BCMath.
Sintaxe
Inteiros podem ser especificados em notação decimal (base 10), hexadecimal (base 16) ou octal (base 8), opcionalmente precedido de sinal (- ou +).
Para usar a notação octal, você precisa preceder o número com um 0 (zero). Para utilizar a notação hexadecimal, preceda número com 0x.
Exemplo #1 Literais inteiras
<?php
$a = 1234; // número decimal
$a = -123; // um número negativo
$a = 0123; // número octal (equivalente a 83 em decimal)
$a = 0x1A; // número hexadecimal (equivalente a 26 em decimal)
?>
decimal : [1-9][0-9]*
| 0
hexadecimal : 0[xX][0-9a-fA-F]+
octal : 0[0-7]+
integer : [+-]?decimal
| [+-]?hexadecimal
| [+-]?octal
Aviso
Se um dígito inválido é passado para inteiro octal (i.e. 8 ou 9), o resto do número é ignorado.
Exemplo #2 Octal weirdness
<?php
var_dump(01090); // 010 octal = 8 decimal
?>
Overflow de inteiros
Se você especifica um número além dos limites do tipo inteiro, ele será interpretado como um ponto flutuante. Assim, se você realizar uma operação que resulte em um número além dos limites do tipo inteiro, um ponto flutuante será retornado também.
<?php
$ numero_grande = 2147483647;
var_dump($numero_grande);
// saida: int(2147483647)
$numero_grande = 2147483648;
var_dump($numero_grande);
// saida: 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)
$milhao = 1000000;
$numero_grande = 50000 * $milhao;
var_dump($numero_grande);
// saida: float(50000000000)
?>
Aviso
Infelizmente, há um bug no PHP que faz que ele nem sempre trabalhe corretamente quando há números negativos envolvidos. Por exemplo, quando você faz -50000 * $milhao, o resultado será -429496728. Entretanto, quando ambos os operadores são positivos, isso não ocorre.
Isto foi resolvido no PHP 4.1.0.
Não há operador de divisão inteira no PHP. 1/2 retorna o ponto flutuante 0.5. Você pode moldar (cast) o valor para inteiro para sempre truncar o número, ou você pode usar a função round().
<?php
var_dump(25/7); // float(3.5714285714286)
var_dump((int) (25/7)); // int(3)
var_dump(round(25/7)); // float(4)
?>
Convertendo para inteiro
Para converter explicitamente um valor para inteiro, utilize-se dos modificadores (int) ou (integer). Entretanto, na maioria dos casos, você não precisa utilizar o modificador, desde que qualquer valor será automaticamente convertido se um operador, função ou estrutura de controle requerer um argumento inteiro. Você também pode converter o valor de um inteiro com a função intval().
Veja também Manipulação de tipos.
de booleanos
FALSE será retornado como 0 (zero), e TRUE como 1 (um).
De números de ponto flutuante
Quando convertendo de números de ponto flutuante para inteiros, o número será truncado.
Se o número convertido estiver além dos limites de um inteiro (usualmente +/- 2.15e+9 = 2^31), o resultado é indefinido, mesmo porque o ponto flutuante não tem a mesma precisão para fornecer um resultado inteiro exato. Não se preocupe, pois nenhum aviso será emitido neste caso!
Aviso
Para maiores informações, veja o alerta
sobre a precisão de número flutuante..
Nunca modifique uma fração desconhecida para inteiro, porque isto pode fornecer resultados inesperados as vezes.
<?php
echo (int) ( (0.1+0.7) * 10 ); // imprime 7!
?>
De strings
De outros tipos
Cuidado
O comportamento da conversão de um inteiro é indefinido de outros tipos. Atualmente, o comportamento é o mesmo como se primeiro o valor fosse convertido para booleano. Entretanto, não confie neste comportamento, pois ele pode mudar sem aviso.
add a note
User Contributed NotesInteiros
dbmuller at gmail dot com
18-Aug-2008 08:43
18-Aug-2008 08:43
rustamabd at gmail dot com
04-Aug-2008 08:45
04-Aug-2008 08:45
Be very careful with code that relies on integer overflow. Negative overflow is handled differently on different platforms. For example, this code:
<?php
echo (int)-3000000000; // a 32bit negative overflow
?>
... outputs 1294967296 on Windows, and -2147483648 on FreeBSD.
(Tested with php 5.2.6, freebsd 7.0)
eric
11-Jun-2008 05:50
11-Jun-2008 05:50
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
winterheat
10-Jun-2008 07:25
10-Jun-2008 07:25
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.
Elliott Brueggeman
07-Feb-2008 01:52
07-Feb-2008 01:52
Don't forget about the integer minimum value. From my experimentation, the lowest valid integer is (PHP_INT_MAX * -1)-1. All values smaller than this fail the is_int() test, even though the may appear to act normally during mathematic operations. More info on this: http://www.ebrueggeman.com/blog/php/integers-and-floating-numbers/
bart at NOvankuikSPAM dot nl
09-Jan-2008 07:06
09-Jan-2008 07:06
When handling very large numbers in PHP, you'll notice they get cut off at hexadecimal 7FFFF FFFF. Sometimes, you don't need to use these numbers in an actual calculation in PHP (i.e. just editing and displaying), and just need to save them in a database.
In that case, you can let MySQL handle the conversion from and to hexadecimal notation. In the example below, engineers need to save hexadecimal addresses up to FFFF FFFF. To update such a value in MySQL, use the following query, where 'addr' is a column with type unsigned integer(10).
<?php
$query = "
UPDATE hardware_register
SET name = ?,
type = ?,
addr = conv(?, 16, 10)
WHERE id = ?
";
?>
And selecting:
<?php
$query = "
SELECT name, type, conv(addr, 10, 16)
FROM hardware_register
WHERE id = ?
";
?>
Note that you'll have to treat the resulting addr column as a string everywhere in PHP. You can't do conversions like:
<?php
$addr_decimal = sprintf("%X", $addr_column);
?>
because that'll result in $addr_decimal having the cut-off, maximum int value.
autotelic at NOOOOSPAM dot hotmail dot com
29-Nov-2007 04:36
29-Nov-2007 04:36
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
darkshire
16-Nov-2007 10:56
16-Nov-2007 10:56
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.
Paul
04-Sep-2007 03:46
04-Sep-2007 03:46
"always round it downwards"
It seems to truncate, or round toward zero, rather than downward. If the float is negative, it is rounded up.
d_n at NOSPAM dot Loryx dot com
13-Aug-2007 09:33
13-Aug-2007 09:33
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]
;
?>
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);
?>
me at troyswanson dot net
12-Jun-2007 07:11
12-Jun-2007 07:11
This note applies to machines that are using a 32 bit integer size. I imagine the same results occur in 64 bit machines as well (with the number 2^63-1).
-2147483648 falls into the range of 32 bit signed integers (0b10000000000000000000000000000000), 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)
?>
Regards
Jacek
10-Mar-2007 09:51
10-Mar-2007 09:51
On 64 bits machines max integer value is 0x7fffffffffffffff (9 223 372 036 854 775 807).
09-Mar-2007 12:26
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'
popefelix at gmail dot com
21-Dec-2006 11:50
21-Dec-2006 11:50
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.
rustamabd@gmail-you-know-what
12-Dec-2006 06:42
12-Dec-2006 06:42
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($i/36)*36)."\n";
?>
Will output:
i=6.88713E+009
i%36=-24
alternative i%36=20
jmw254 at cornell dot edu
25-Aug-2006 02:14
25-Aug-2006 02:14
Try this one instead:
function iplongtostring($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";
}
rickard_cedergren at yahoo dot com
27-Jan-2005 06:15
27-Jan-2005 06:15
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) + $fix / 256 / 256
)
);
}
else {
return('');
}
}
23-Dec-2003 03:18
Sometimes you need to parse an unsigned
32 bit integer. Here's a function I 've used:
function parse_unsigned_int($string) {
$x = (float)$string;
if ($x > (float)2147483647)
$x -= (float)"4294967296";
return (int)$x;
}