PHP的ip2long 是将IP地址转换为数值的函数。
ip2long() 转出来的数值应该都是正整数,但是在某些机器转出负数, 刚开始以为是 PHP 版本问题, 后来做些测试, 确定是系统版本 32bits 和 64bits 的问题。
32 bits ip2long(): -2147483648 ~ 214748364764
64 bits ip2long(): 0 ~ 42949672945
测试代码:
3 | list( $a , $b , $c , $d ) = split( "." , $ip ); |
4 | $ip_long = (( $a * 256 + $b ) * 256 + $c ) * 256 + $d ; |
另外做测试,在return值加上intval(), 如下述:
3 | list( $a , $b , $c , $d ) = split( "." , $ip ); |
4 | $ip_long = (( $a * 256 + $b ) * 256 + $c ) * 256 + $d ; |
5 | return intval ( $ip_long ); |
intval在32bits/64 bits最大值是不同的,于intval()里面有写到下述:
The maximum value depends on the system.
32 bit systems have a maximum signed integer range of -2147483648 to 2147483647.
So for example on such a system, intval("1000000000000") will return 2147483647.
The maximum signed integer value for 64 bit systems is 9223372036854775807.
另外做其它测试:
02 | ip2long ( "127.255.255.255" ); |
03 | ip2long ( "255.255.255.255" ); |
04 | ip2long ( "255.255.255.254" ); |
05 | ip2long ( "192.168.1.2" ); |
06 | ip2long () 于 64bits 的系统测试 |
07 | ip2long ( "127.255.255.255" ); |
08 | ip2long ( "255.255.255.255" ); |
09 | ip2long ( "255.255.255.254" ); |
10 | ip2long ( "192.168.1.2" ); |
解法1 - 自己转换
2 | list( $a , $b , $c , $d ) = explode( "." , $ip ); |
3 | return (( $a * 256 + $b ) * 256 + $c ) * 256 + $d ; |
解法2 - 转成二进制, 再转回十进制
3 | echo bindec ( decbin ( ip2long ( "192.168.1.2" ))); |
解法3 - 官方建议的解法 (推荐用此方法)
2 | printf( "%u" , ip2long ( "192.168.1.2" )); |
4 | echo sprintf( "%u" , ip2long ( "192.168.1.2" )); |
关于第一种方法,从数值转换回IP可以使用下面的参考代码(如果数特别大,在32bits下就不是整数,是浮点数,求余那个地方会出负数):
1 | function longtoip( $num ) { |
3 | $c = (( $num - $d )/256)%256; |
4 | $b = (( $num -( $c *256)- $d )/(256*256))%256; |
5 | $a = (( $num -( $b *256*256)- $c *256- $d )/(256*256*256))%256; |
6 | return $a . "." . $b . "." . $c . "." . $d ; } |
来源:http://blog.csdn.net/everything1209/article/details/22418559