php 两个无限位数长度数的加减乘除算法 

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<?php
//用字符串存放需要计算的数字
$var1 = '1812333333333333333333333333333312312312365465115168798845654646546541654623645654654132165798498799935965878749878990802045729820438846724720077549820225200070877958874065976960871699930588877830002524992671885461625646546546546546546126154654654';
$var2 = '2364565465413216579849879812363254541654565746871239648712653441235461243465142635441623141233241132234461523446512341236454126344612534';
$result = countNum($var1, $var2);

$maxLength = count($result);
for( $num = $maxLength - 1; $num >= 0; $num-- ){
    echo $result[$num];
}

/**
 * @name 计算两个数的加法
 * @author geekzhumail@gmail.com
 * @since 2014-03-16
 * @param var1 第一个数字
 * @param var2 第二个数字
 */
function countNum( $var1, $var2 ){
    $result = array();//结果
    $var1Length = strlen( $var1 );
    $var2Length = strlen( $var2 );
    $maxLength = ($var1Length >= $var2Length )?$var1Length:$var2Length;
    $temp = 0;
    $num = 0;
    while( true ){
        $temp1 = ($num >= $var1Length )?0:$var1[$var1Length - $num - 1];
        $temp2 = ($num >= $var2Length )?0:$var2[$var2Length - $num - 1];
        $temp += $temp1 + $temp2;
        $temp = str_split($temp);
        //var_dump($temp);
        //exit;
        $result[$num] = ( count( $temp ) > 1 )?$temp[1]:$temp[0];
        $temp = ( count( $temp ) > 1 )?$temp[0]:0;
        $num++;
        if( $num == $maxLength ){
            if( $temp != 0 ) {
                $result[$num] = $temp;
            }
            break;
        }
    }
    return $result;
}