PHP - Manual: gmp_init

2024-12-23

gmp_intval »

« gmp_import

gmp_init

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

gmp_init — Create GMP number

说明

gmp_init(int|string $num, int $base = 0): GMP

Creates a GMP number from an integer or string.

参数

num

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

base

The base.

The base may vary from 2 to 62. If base is 0 (default value), the actual base is determined from the leading characters: if the first two characters are 0x or 0X, hexadecimal is assumed, if the first two characters are 0b or 0B, binary is assumed, otherwise if the first character is 0, octal is assumed, otherwise decimal is assumed. For bases up to 36, case is ignored; upper-case and lower-case letters have the same value. For bases 37 to 62, upper-case letter represent the usual 10 to 35 while lower-case letter represent 36 to 61.

返回值

GMP 对象。

范例

示例 #1 Creating GMP number


<?php
$a = gmp_init(123456);
$b = gmp_init("0xFFFFDEBACDFEDF7200");
?>

注释

注意:
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().

add a note

User Contributed Notes 7 notes

down

php at richardneill dot org ¶

15 years ago


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

<?
if (preg_match("/^[0-9]+\.[0-9]+$/",$input)){ 
     //Input is a base-10 decimal. Multiply as necessary to remove the decimal
     //point. Convert that to a gmp_resource, then decrement the exponent 
     //to compensate.

     $pieces=explode(".", $input);     //Split at the d.p.
     $input="$pieces[0]$pieces[1]";  //Remove the decimal point.

     $input=ltrim($input,'0');    
     //Remove any leading zeros, or gmp_init will parse the number as octal.

     if ($input==''){    //Deal with "0.0" which would otherwise be ''.
          $input=0;
      }
      $integer=gmp_init($input);   
      $ns_exponent=-strlen($pieces[1]);  
     //exponent = (-)  the number of characters after the decimal point.
}
?>

down

karl dot debisschop at pearson dot com ¶

11 years ago


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

down

marcus at synchromedia dot co dot uk ¶

10 years ago


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.

down

php at richardneill dot org ¶

15 years ago


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.

down

Aurelien Marchand ¶

1 month ago


Missing from the documentation: gmp_init() return false in case it failed to parse $num

<?php
var_dump(gmp_init(""));
// returns "bool(false)" and not a GMP object as hinted by the documentation, it also triggers a Warning "PHP Warning:  gmp_init(): Unable to convert variable to GMP - string is not an integer in php shell code on line 1"

?>

down

-1

charlie at oblivion dot cz ¶

15 years ago


gmp_* functions don't accept strings with a leading '+':
<?php
echo gmp_strval(gmp_init('+42'));      #0
echo gmp_strval(gmp_add('42', '+42')); #42
echo bcadd('+42', '+42');              #84
?>

down

-3

thomas dot hebinck at digionline dot de ¶

16 years ago


If you call a gmp_* function directly with an interger as parameter, this integer MUST NOT be 0:

for($i=-1;$i<=1;$i++) {  echo gmp_strval(gmp_add(2,gmp_mul(1,$i))) . ' ';  }

The result is 1 0 3 (wrong)

In this case you have to use gmp_init():

for($i=-1;$i<=1;$i++) {  echo gmp_strval(gmp_add(2,gmp_mul(1,gmp_init($i)))) . ' ';  }

The result is 1 2 3 (right)

Happy number crunching! :-)

add a note

官方地址：https://www.php.net/manual/en/function.gmp-init.php

有任何技术问题请点击这里网站运营推广招聘

IT PHP 编程语言 Linux 开发编程科技 Elasticsearch HTML/CSS/XML 网络数据库 JAVA 面试 NoSQL C/C++ Golang Git 算法操作系统正则表达式 Redis 互联网 MySql JavaScript 运维软件国际架构设计 Mac OS TCP/IP Excel Vim Windows Socket Oracle VR MongoDB Python 运营 MemCache 商业硬件电子娱乐设计 nginx 摄影游戏 WordPress HTTP 团建数码电器

php7 安装fileinfo扩展 preg_split — 通过一个正则表达式分隔字符串 php位值,解决 PHP 中 usort 在值相同时改变原始位置的问题 [PHP] inet_pton/inet_ntop IP地址转换函数 [鸟哥]PHP_INT_MIN 和 -9223372036854775808 PHP 8.1 ADORecordSet对象 adodb手册 opcache预加载 Composer的Packagist资源 array_multisort() 多字段排序 mysql面试题 PHPMailer设置utf8 PHPMailer字符集CharSet PHP json解析（json_decode）页面工具 php中几种注释规范 [原创]诡异的php-fpm超时问题 PHP获取指定函数定义在哪个文件中及行号 php上周一、本周一、下周一日期 [鸟哥]PHP FFI详解 - 一种全新的PHP扩展方式 php扩展开发

略微加速

PHP官方手册 - 互联网笔记

gmp_init

说明

参数

返回值

范例

注释

User Contributed Notes 7 notes