Булев тип
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;
?>
Целочислен тип
Целочислено е всяко число от множеството Z = {..., -2, -1, 0, 1, 2, ...}.
Вж. също: Цели числа с произволна дължина / GMP, Числа с плаваща запетая и Произволна точност / BCMath
Синтаксис
Целите числа могат да бъдат дефинирани в десетична (с основа 10), шестнайсетична (с основа 16) или осмична (с основа 8) бройна система, незадължително предшествани от знак (- или +).
Ако използвате осмична бройна система, трябва да предшествате числото с 0 (нула), а за да използвате шестнайсетична система, трябва да го предшествате с 0x.
Example #1 Целочислени литерали
<?php
$a = 1234; // десетично число
$a = -123; // отрицателно число
$a = 0123; // осмично число (еквивалентно на десетично 83)
$a = 0x1A; // шестнайсетично число (еквивалентно на десетично 26)
?>
десетично : [1-9][0-9]*
| 0
шестнадесетично : 0[xX][0-9a-fA-F]+
осмично : 0[0-7]+
цяло число : [+-]?decimal
| [+-]?hexadecimal
| [+-]?octal
Предупреждение
Ако на осмично число бъде подадена невалидна цифра (т.е. 8 или 9), остатъкът от числото ще бъде пренебрегнат.
Example #2 Осмична особеност
<?php
var_dump(01090); // осмично 010 = десетично 8
?>
Целочислено препълване
Ако укажете число извън обхвата на целочисления тип, то ще бъде интерпретирано като число с плаваща запетая. Също така, ако извършите операция, чийто резултат е число извън обхвата на целочисления тип, то също ще бъде върнато в плаващ тип.
<?php
$large_number = 2147483647;
var_dump($large_number);
// изход: int(2147483647)
$large_number = 2147483648;
var_dump($large_number);
// изход: float(2147483648)
// работи също за цели числа, указани в шестнадесетична система, в интервала от 2^31 до 2^32-1:
var_dump( 0xffffffff );
// output: float(4294967295)
// не работи за цели числа, указани в шестнадесетична система, за стойности над 2^32-1:
var_dump( 0x100000000 );
// изход: int(2147483647)
$million = 1000000;
$large_number = 50000 * $million;
var_dump($large_number);
// изход: float(50000000000)
?>
Предупреждение
За нещастие, в PHP съществуваше грешка, така че това не работи винаги както трябва, когато са намесени отрицателни числа. Например: когато правите -50000 * $million, резултатът ще бъде -429496728. Все пак, когато и двата операнда са положителни, няма проблем.
Грешката е поправена в PHP 4.1.0.
В PHP няма оператор за целочислено деление. 1/2 дава плаващо 0.5. Можете да преобразувате стойността до цяло число, така че тя винаги да се закръгля надолу, или пък да използвате функцията round().
<?php
var_dump(25/7); // float(3.5714285714286)
var_dump((int) (25/7)); // int(3)
var_dump(round(25/7)); // float(4)
?>
Преобразуване в цяло число
За да превърнете изрично стойност в цяло число, използвайте преобразуването (int) или (integer). В повечето случаи обаче няма нужда да се използва преобразуване, понеже стойността ще бъде преобразувана автоматично, когато даден оператор, функция или контролна структура изискват целочислен аргумент. Можете също да превърнете стойност в цяло число посредством функцията intval().
Вж. също Манипулации с типове.
От булев
FALSE ще даде 0 (нула), а TRUE ще даде 1 (едно).
От числа с плаваща запетая
При превръщане от плаващо в цяло, числото ще бъде закръглено към нулата (надолу).
Ако плаващото е извън обхвата на цяло число (обикновено +/- 2.15e+9 = 2^31), резултатът е недефиниран, тъй като плаващото не е имало достатъчно точност, за да даде правилен целочислен резултат. В този случай няма да бъде изведено нито предупреждение, нито дори и съобщение!
Предупреждение
За повече информация, вижте предупреждението за
плаваща точност.
Никога не преобразувайте неизвестна дроб в цяло число, защото понякога това може да доведе до неочаквани резултати.
<?php
echo (int) ( (0.1+0.7) * 10 ); // извежда 7!
?>
От низове
От други типове
Внимание
Поведението при превръщане от други типове в цяло число е недефинирано. В момента, поведението е същото, както ако стойността първо е била превърната в булев. Все пак, не разчитайте на това поведение, тъй като в бъдеще то може да се промени без предупреждение.
add a note
User Contributed NotesЦелочислен тип
dbmuller at gmail dot com
19-Aug-2008 01:43
19-Aug-2008 01:43
rustamabd at gmail dot com
04-Aug-2008 01:45
04-Aug-2008 01:45
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 10:50
11-Jun-2008 10:50
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
11-Jun-2008 12:25
11-Jun-2008 12:25
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 04:52
07-Feb-2008 04:52
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 10:06
09-Jan-2008 10:06
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 07:36
29-Nov-2007 07:36
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 01:56
16-Nov-2007 01:56
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 08:46
04-Sep-2007 08:46
"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 02:33
13-Aug-2007 02:33
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 12:11
12-Jun-2007 12:11
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 01:51
10-Mar-2007 01:51
On 64 bits machines max integer value is 0x7fffffffffffffff (9 223 372 036 854 775 807).
09-Mar-2007 04:26
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 03:50
21-Dec-2006 03:50
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 10:42
12-Dec-2006 10:42
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($i/36)*36)."\n";
?>
Will output:
i=6.88713E+009
i%36=-24
alternative i%36=20
jmw254 at cornell dot edu
25-Aug-2006 07:14
25-Aug-2006 07:14
Try this one instead:
function iplongtostring($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 10:15
27-Jan-2005 10:15
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) + $fix / 256 / 256
)
);
}
else {
return('');
}
}
23-Dec-2003 07:18
Sometimes you need to parse an unsigned
32 bit integer. Here's a function I 've used:
function parse_unsigned_int($string) {
$x = (float)$string;
if ($x > (float)2147483647)
$x -= (float)"4294967296";
return (int)$x;
}