PHP代码
$id = intval($_GET['id']);
intval
(PHP 4, PHP 5)
intval ― Get the integer value of a variable
Description
int intval ( mixed $var [, int $base= 10 ] )
Returns the integer value of var , using the specified base for the conversion (the default is base 10).
Parameters
var
The scalar value being converted to an integer
base
The base for the conversion (default is base 10)
Return Values
The integer value of var on success, or 0 on failure. Empty arrays and objects return 0, non-empty arrays and objects return 1.
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.
Strings will most likely return 0 although this depends on the leftmost characters of the string. The common rules of integer casting apply.
Examples

<?php 
echo intval(42); // 42 
echo intval(4.2); // 4 
echo intval('42'); // 42 
echo intval('+42'); // 42 
echo intval('-42'); // -42 
echo intval(042); // 34 
echo intval('042'); // 42 
echo intval(1e10); // 1410065408 
echo intval('1e10'); // 1 
echo intval(0x1A); // 26 
echo intval(42000000); // 42000000 
echo intval(420000000000000000000); // 0 
echo intval('420000000000000000000'); // 2147483647 
echo intval(42, 8); // 42 
echo intval('42', 8); // 34 
?>