布尔型
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;
?>
整型
一个 integer 是集合 Z = {..., -2, -1, 0, 1, 2, ...} 中的一个数。
参见任意长度整数（GMP），浮点数和任意精度数学库（BCMath）。
语法
整型值可以用十进制，十六进制或八进制符号指定，前面可以加上可选的符号（- 或者 +）。
如果用八进制符号，数字前必须加上 0（零），用十六进制符号数字前必须加上 0x。
Example#1 整数文字表达
<?php
$a = 1234; // 十进制数
$a = -123; // 一个负数
$a = 0123; // 八进制数（等于十进制的 83）
$a = 0x1A; // 十六进制数（等于十进制的 26）
?>
decimal : [1-9][0-9]*
| 0
hexadecimal : 0[xX][0-9a-fA-F]+
octal : 0[0-7]+
integer : [+-]?decimal
| [+-]?hexadecimal
| [+-]?octal
Warning
如果向八进制数传递了一个非法数字（即 8 或 9），则后面其余数字会被忽略。
Example#2 八进制数的怪事
<?php
var_dump(01090); // 010 octal = 8 decimal
?>
整数溢出
如果给定的一个数超出了 integer 的范围，将会被解释为 float。同样如果执行的运算结果超出了 integer 范围，也会返回 float。
<?php
$large_number = 2147483647;
var_dump($large_number);
// 输出为：int(2147483647)
$large_number = 2147483648;
var_dump($large_number);
// 输出为：float(2147483648)
// 同样也适用于十六进制表示的整数：
var_dump( 0x80000000 );
// 输出为：float(2147483648)
$million = 1000000;
$large_number = 50000 * $million;
var_dump($large_number);
// 输出为：float(50000000000)
?>
Warning
不幸的是 PHP 中有个 bug，因此当有负数参与时结果并不总是正确。例如当运算 -50000 * $million 时结果是 -429496728。不过当两个运算数都是正数时就没问题。
这个问题已经在 PHP 4.1.0 中解决了。
PHP 中没有整除的运算符。1/2 产生出 float 0.5。可以总是舍弃小数部分，或者使用 round() 函数。
<?php
var_dump(25/7); // float(3.5714285714286)
var_dump((int) (25/7)); // int(3)
var_dump(round(25/7)); // float(4)
?>
转换为整形
要明示地将一个值转换为 integer，用 (int) 或 (integer) 强制转换。不过大多数情况下都不需要强制转换，因为当运算符，函数或流程控制需要一个 integer 参数时，值会自动转换。还可以通过函数 intval() 来将一个值转换成整型。
参见类型戏法。
从布尔值转换
FALSE 将产生出 0（零），TRUE 将产生出 1（壹）。
从浮点数转换
当从浮点数转换成整数时，数字将被取整（丢弃小数位）。
如果浮点数超出了整数范围（通常为 +/- 2.15e+9 = 2^31），则结果不确定，因为没有足够的精度使浮点数给出一个确切的整数结果。在此情况下没有警告，甚至没有任何通知！
【译者注】在 Linux 下返回结果是最小负数（-2147483648），而在 Windows 下返回结果是零（0）。
从字符串转换
参见字符串转换为数字。
从其它类型转换
Caution
没有定义从其它类型转换为整型的行为。目前的行为和值先转换为布尔值一样。不过不要依靠此行为，因为它会未加通知地改变。
add a note
User Contributed Notes整型
dbmuller at gmail dot com
19-Aug-2008 07:43
19-Aug-2008 07:43
rustamabd at gmail dot com
04-Aug-2008 07:45
04-Aug-2008 07:45
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
12-Jun-2008 04:50
12-Jun-2008 04:50
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 06:25
11-Jun-2008 06:25
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 11:52
07-Feb-2008 11:52
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 05:06
09-Jan-2008 05:06
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
30-Nov-2007 02:36
30-Nov-2007 02:36
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 08:56
16-Nov-2007 08:56
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
05-Sep-2007 02:46
05-Sep-2007 02:46
"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 08:33
13-Aug-2007 08:33
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 06:11
12-Jun-2007 06:11
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 08:51
10-Mar-2007 08:51
On 64 bits machines max integer value is 0x7fffffffffffffff (9 223 372 036 854 775 807).
09-Mar-2007 11:26
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 10:50
21-Dec-2006 10:50
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
13-Dec-2006 05:42
13-Dec-2006 05:42
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($i/36)*36)."\n";
?>
Will output:
i=6.88713E+009
i%36=-24
alternative i%36=20
jmw254 at cornell dot edu
26-Aug-2006 01:14
26-Aug-2006 01:14
Try this one instead:
function iplongtostring($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 05:15
27-Jan-2005 05:15
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) + $fix / 256 / 256
)
);
}
else {
return('');
}
}
24-Dec-2003 02:18
Sometimes you need to parse an unsigned
32 bit integer. Here's a function I 've used:
function parse_unsigned_int($string) {
$x = (float)$string;
if ($x > (float)2147483647)
$x -= (float)"4294967296";
return (int)$x;
}