计算时指定精度，适用于计算财务

dec_calc.php

<?php

function dec_calc($a, $b, $p, $func, $fp)
{
    for ($m=1,$i=0; $i < $p; $i++) { 
        $m *= 10;
    }
    $aa = $a*$m;
    $bb = $b*$m;
    $r = $func($aa, $bb);
    for ($d=1,$i=0; $i < $fp; $i++) { 
        $d *= $m;
    }
    return round($r / $d, $p);
}

function logs($str, $level)
{
    echo "<p>$str</p>\n";
}

function dec_add($a, $b, $p)
{
    return dec_calc($a, $b, $p, function($a,$b){return $a+$b}, 1);
}

function dec_sub($a, $b, $p)
{
    return dec_calc($a, $b, $p, function($a,$b){return $a-$b}, 1);
}

function dec_multi($a, $b, $p)
{
    return dec_calc($a, $b, $p, function($a,$b){return $a*$b}, 2);
}

function dec_div($a, $b, $p)
{
    return dec_calc($a, $b, $p, function($a,$b){return $a/$b}, 0);
}

var_dump(
    dec_calc(
        dec_calc(
            0.1,
            0.72,
            2,
            function ($a, $b) {return $a+$b;},
            1
        ),
        10,
        2,
        function ($a, $b) {return $a*$b;},
        2
    )
);

MoneyDec.php

<?php

/**
* 
*/
class MoneyDec
{
    public $val;
    public $pr;
    public $int;
    public function __construct($val, $pr)
    {
        $this->int = $this->val = $val;
        $this->pr = $pr;
        for ($this->m=1, $i=0; $i < $pr; $i++) { 
            $this->int *= 10;
            $this->m *= 10;
        }
        $this->int = (int) round($this->int);
    }
    public function __s
}

function dec_add(MoneyDec $a, MoneyDec $b)
{
    $aint = $a->int;
    $bint = $b->int;
    // 对齐
    // 寻找小的，乘以商
    if ($a->pr == $b->pr) {
    } elseif ($a->pr < $b->pr) {
        $aint *= $b->m / $a->m;
    } else {
        $bint *= $a->m / $b->m;
    }
    $rint = $aint + $bint;
    return new MoneyDec($rint / max($a->m, $b->m), max($a->pr, $b->pr));
}

function logs($str, $level)
{
    echo "<p>$str</p>\n";
}

$a = new MoneyDec(0.1, 8);
$b = new MoneyDec(0.7, 2);
$c = dec_add($a, $b, function($a,$b){return $a+$b;});
var_dump($c);