gmp_init()

(PHP 4 >= 4.0.4, PHP 5, PHP 7)

Create GMP number

说明

Creates a GMP number from an integer or string.

参数

An integer or a string. The string representation can be decimal, hexadecimal or octal.

The base.

The base may vary from 2 to 36. If base is 0(default value), the actual base is determined from the leading characters: if the first two characters are0xor0X, hexadecimal is assumed, otherwise if the first character is "0", octal is assumed, otherwise decimal is assumed.

返回值

GMP 数值资源.

更新日志

注释

To use the extended base introduced in PHP 5.3.2, then PHP must be compiled against GMP 4.2.0 or greater.

范例

Creating GMP number

注释

It is not necessary to call this function in order to use integers or strings in place of GMP numbers in GMP functions(such as with gmp_add()). Function arguments are automatically converted to GMP numbers, if such conversion is possible and needed, using the same rules as gmp_init().

I discovered that the gmp functions use [0-9a-f] up to base 16, but [0-9A-Za-z] (i.e. upper case first) from bases 17 to 62. This differs from most of the base-62 implementations I've found that tend to use lower case first.

Here's a way to parse a decimal (eg 3.25) into an integer and exponent: 

Note: Leading zeros will make gmp_init parse this as octal.
Thus gmp_init(010) becomes 8. 
$a=010;       //8
$b="010" + 0;   //10
$c=gmp_strval(gmp_init(010));  //8
$d=gmp_strval(gmp_init("010")); //8
This behaviour is inconsistent: either $d should equal $b, or
$b should equal $a.

Unless the base is 16, gpm_init will fail if the string begins with "0b". 
> php -r '$v = gmp_init("b83", 17); print("$v\n");'
Resource id #4
> php -r '$v = gmp_init("0b83", 17); print("$v\n");'
[nothing prints]
In may case, where I am explicitly specifying the base, the solution is to apply ltrim first:
> php -r '$v = gmp_init(ltrim("0b83", "0"), 17); print("$v\n");'
Resource id #4

gmp_* functions don't accept strings with a leading '+': 

If you call a gmp_* function directly with an interger as parameter, this integer MUST NOT be 0:
for($i=-1;$i

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