PHP: fmod - Manual (original) (raw)

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

fmod — Returns the floating point remainder (modulo) of the division of the arguments

Description

Parameters

num1

The dividend

num2

The divisor

Return Values

The floating point remainder of num1/num2

Examples

Example #1 Using fmod()

<?php $x = 5.7; <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mo>=</mo><mn>1.3</mn><mo separator="true">;</mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>k</mi><mi>a</mi><mi>t</mi><mi>e</mi><mi>x</mi><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>k</mi><mi>a</mi><mi>t</mi><mi>e</mi><mi>x</mi><mo>−</mo><mi>m</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>m</mi><mi>l</mi><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi>m</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>x</mi><mi>m</mi><mi>l</mi><mi>n</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>h</mi><mi>t</mi><mi>t</mi><mi>p</mi><mo>:</mo><mi mathvariant="normal">/</mi><mi mathvariant="normal">/</mi><mi>w</mi><mi>w</mi><mi>w</mi><mi mathvariant="normal">.</mi><mi>w</mi><mn>3.</mn><mi>o</mi><mi>r</mi><mi>g</mi><mi mathvariant="normal">/</mi><mn>1998</mn><mi mathvariant="normal">/</mi><mi>M</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi mathvariant="normal">/</mi><mi>M</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>M</mi><mi>L</mi><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi>s</mi><mi>e</mi><mi>m</mi><mi>a</mi><mi>n</mi><mi>t</mi><mi>i</mi><mi>c</mi><mi>s</mi><mo>></mo><mo><</mo><mi>m</mi><mi>r</mi><mi>o</mi><mi>w</mi><mo>></mo><mo><</mo><mi>m</mi><mi>i</mi><mo>></mo><mi>r</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>i</mi><mo>></mo><mo><</mo><mi>m</mi><mi>o</mi><mo>></mo><mo>=</mo><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>o</mi><mo>></mo><mo><</mo><mi>m</mi><mi>i</mi><mo>></mo><mi>f</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>i</mi><mo>></mo><mo><</mo><mi>m</mi><mi>i</mi><mo>></mo><mi>m</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>i</mi><mo>></mo><mo><</mo><mi>m</mi><mi>i</mi><mo>></mo><mi>o</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>i</mi><mo>></mo><mo><</mo><mi>m</mi><mi>i</mi><mo>></mo><mi>d</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>i</mi><mo>></mo><mo><</mo><mi>m</mi><mi>o</mi><mi>s</mi><mi>t</mi><mi>r</mi><mi>e</mi><mi>t</mi><mi>c</mi><mi>h</mi><mi>y</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>f</mi><mi>a</mi><mi>l</mi><mi>s</mi><mi>e</mi><mi mathvariant="normal">"</mi><mo>></mo><mo stretchy="false">(</mo><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>o</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>r</mi><mi>o</mi><mi>w</mi><mo>></mo><mo><</mo><mi>a</mi><mi>n</mi><mi>n</mi><mi>o</mi><mi>t</mi><mi>a</mi><mi>t</mi><mi>i</mi><mi>o</mi><mi>n</mi><mi>e</mi><mi>n</mi><mi>c</mi><mi>o</mi><mi>d</mi><mi>i</mi><mi>n</mi><mi>g</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>a</mi><mi>p</mi><mi>p</mi><mi>l</mi><mi>i</mi><mi>c</mi><mi>a</mi><mi>t</mi><mi>i</mi><mi>o</mi><mi>n</mi><mi mathvariant="normal">/</mi><mi>x</mi><mo>−</mo><mi>t</mi><mi>e</mi><mi>x</mi><mi mathvariant="normal">"</mi><mo>></mo><mi>r</mi><mo>=</mo><mi>f</mi><mi>m</mi><mi>o</mi><mi>d</mi><mo stretchy="false">(</mo><mo><</mo><mi mathvariant="normal">/</mi><mi>a</mi><mi>n</mi><mi>n</mi><mi>o</mi><mi>t</mi><mi>a</mi><mi>t</mi><mi>i</mi><mi>o</mi><mi>n</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>e</mi><mi>m</mi><mi>a</mi><mi>n</mi><mi>t</mi><mi>i</mi><mi>c</mi><mi>s</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>m</mi><mi>a</mi><mi>t</mi><mi>h</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>k</mi><mi>a</mi><mi>t</mi><mi>e</mi><mi>x</mi><mo>−</mo><mi>h</mi><mi>t</mi><mi>m</mi><mi>l</mi><mi mathvariant="normal">"</mi><mi>a</mi><mi>r</mi><mi>i</mi><mi>a</mi><mo>−</mo><mi>h</mi><mi>i</mi><mi>d</mi><mi>d</mi><mi>e</mi><mi>n</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>t</mi><mi>r</mi><mi>u</mi><mi>e</mi><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>b</mi><mi>a</mi><mi>s</mi><mi>e</mi><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>s</mi><mi>t</mi><mi>r</mi><mi>u</mi><mi>t</mi><mi mathvariant="normal">"</mi><mi>s</mi><mi>t</mi><mi>y</mi><mi>l</mi><mi>e</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>h</mi><mi>e</mi><mi>i</mi><mi>g</mi><mi>h</mi><mi>t</mi><mo>:</mo><mn>0.4306</mn><mi>e</mi><mi>m</mi><mo separator="true">;</mo><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>o</mi><mi>r</mi><mi>d</mi><mi>m</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>n</mi><mi>o</mi><mi>r</mi><mi>m</mi><mi>a</mi><mi>l</mi><mi mathvariant="normal">"</mi><mi>s</mi><mi>t</mi><mi>y</mi><mi>l</mi><mi>e</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>a</mi><mi>r</mi><mi>g</mi><mi>i</mi><mi>n</mi><mo>−</mo><mi>r</mi><mi>i</mi><mi>g</mi><mi>h</mi><mi>t</mi><mo>:</mo><mn>0.02778</mn><mi>e</mi><mi>m</mi><mo separator="true">;</mo><mi mathvariant="normal">"</mi><mo>></mo><mi>r</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>c</mi><mi>e</mi><mi mathvariant="normal">"</mi><mi>s</mi><mi>t</mi><mi>y</mi><mi>l</mi><mi>e</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>a</mi><mi>r</mi><mi>g</mi><mi>i</mi><mi>n</mi><mo>−</mo><mi>r</mi><mi>i</mi><mi>g</mi><mi>h</mi><mi>t</mi><mo>:</mo><mn>0.2778</mn><mi>e</mi><mi>m</mi><mo separator="true">;</mo><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>r</mi><mi>e</mi><mi>l</mi><mi mathvariant="normal">"</mi><mo>></mo><mo>=</mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>c</mi><mi>e</mi><mi mathvariant="normal">"</mi><mi>s</mi><mi>t</mi><mi>y</mi><mi>l</mi><mi>e</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>a</mi><mi>r</mi><mi>g</mi><mi>i</mi><mi>n</mi><mo>−</mo><mi>r</mi><mi>i</mi><mi>g</mi><mi>h</mi><mi>t</mi><mo>:</mo><mn>0.2778</mn><mi>e</mi><mi>m</mi><mo separator="true">;</mo><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>b</mi><mi>a</mi><mi>s</mi><mi>e</mi><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>s</mi><mi>t</mi><mi>r</mi><mi>u</mi><mi>t</mi><mi mathvariant="normal">"</mi><mi>s</mi><mi>t</mi><mi>y</mi><mi>l</mi><mi>e</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>h</mi><mi>e</mi><mi>i</mi><mi>g</mi><mi>h</mi><mi>t</mi><mo>:</mo><mn>1</mn><mi>e</mi><mi>m</mi><mo separator="true">;</mo><mi>v</mi><mi>e</mi><mi>r</mi><mi>t</mi><mi>i</mi><mi>c</mi><mi>a</mi><mi>l</mi><mo>−</mo><mi>a</mi><mi>l</mi><mi>i</mi><mi>g</mi><mi>n</mi><mo>:</mo><mo>−</mo><mn>0.25</mn><mi>e</mi><mi>m</mi><mo separator="true">;</mo><mi mathvariant="normal">"</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>o</mi><mi>r</mi><mi>d</mi><mi>m</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>n</mi><mi>o</mi><mi>r</mi><mi>m</mi><mi>a</mi><mi>l</mi><mi mathvariant="normal">"</mi><mi>s</mi><mi>t</mi><mi>y</mi><mi>l</mi><mi>e</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>a</mi><mi>r</mi><mi>g</mi><mi>i</mi><mi>n</mi><mo>−</mo><mi>r</mi><mi>i</mi><mi>g</mi><mi>h</mi><mi>t</mi><mo>:</mo><mn>0.10764</mn><mi>e</mi><mi>m</mi><mo separator="true">;</mo><mi mathvariant="normal">"</mi><mo>></mo><mi>f</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>o</mi><mi>r</mi><mi>d</mi><mi>m</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>n</mi><mi>o</mi><mi>r</mi><mi>m</mi><mi>a</mi><mi>l</mi><mi mathvariant="normal">"</mi><mo>></mo><mi>m</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>o</mi><mi>r</mi><mi>d</mi><mi>m</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>n</mi><mi>o</mi><mi>r</mi><mi>m</mi><mi>a</mi><mi>l</mi><mi mathvariant="normal">"</mi><mo>></mo><mi>o</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>o</mi><mi>r</mi><mi>d</mi><mi>m</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>n</mi><mi>o</mi><mi>r</mi><mi>m</mi><mi>a</mi><mi>l</mi><mi mathvariant="normal">"</mi><mo>></mo><mi>d</mi><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mi>c</mi><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo>=</mo><mi mathvariant="normal">"</mi><mi>m</mi><mi>o</mi><mi>p</mi><mi>e</mi><mi>n</mi><mi mathvariant="normal">"</mi><mo>></mo><mo stretchy="false">(</mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mo><</mo><mi mathvariant="normal">/</mi><mi>s</mi><mi>p</mi><mi>a</mi><mi>n</mi><mo>></mo><mi>x</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">y = 1.3; <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi><mo>=</mo><mi>f</mi><mi>m</mi><mi>o</mi><mi>d</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">r = fmod(</annotation></semantics></math>r=fmod(x, </annotation></semantics></math>y=1.3;<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi><mo>=</mo><mi>f</mi><mi>m</mi><mi>o</mi><mi>d</mi><mostretchy="false">(</mo></mrow><annotationencoding="application/x−tex">r=fmod(</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal"style="margin−right:0.02778em;">r</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:1em;vertical−align:−0.25em;"></span><spanclass="mordmathnormal"style="margin−right:0.10764em;">f</span><spanclass="mordmathnormal">m</span><spanclass="mordmathnormal">o</span><spanclass="mordmathnormal">d</span><spanclass="mopen">(</span></span></span></span>x,y); // <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi><mi>e</mi><mi>q</mi><mi>u</mi><mi>a</mi><mi>l</mi><mi>s</mi><mn>0.5</mn><mo separator="true">,</mo><mi>b</mi><mi>e</mi><mi>c</mi><mi>a</mi><mi>u</mi><mi>s</mi><mi>e</mi><mn>4</mn><mo>∗</mo><mn>1.3</mn><mo>+</mo><mn>0.5</mn><mo>=</mo><mn>5.7</mn><mi>v</mi><mi>a</mi><msub><mi>r</mi><mi>d</mi></msub><mi>u</mi><mi>m</mi><mi>p</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">r equals 0.5, because 4 * 1.3 + 0.5 = 5.7var_dump(</annotation></semantics></math>requals0.5,because4∗1.3+0.5=5.7vardump(x, <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">y, </annotation></semantics></math>y,r); ?>

Found A Problem?

jphansen at uga dot edu ¶

20 years ago

fmod() does not mirror a calculator's mod function. For example, fmod(.25, .05) will return .05 instead of 0 due to floor(). Using the aforementioned example, you may get 0 by replacing floor() with round() in a custom fmod().

<?
function fmod_round($x, $y) {
    <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi><mo>=</mo><mi>r</mi><mi>o</mi><mi>u</mi><mi>n</mi><mi>d</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">i = round(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6595em;"></span><span class="mord mathnormal">i</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">ro</span><span class="mord mathnormal">u</span><span class="mord mathnormal">n</span><span class="mord mathnormal">d</span><span class="mopen">(</span></span></span></span>x / $y);
    return <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>−</mo></mrow><annotation encoding="application/x-tex">x - </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6667em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">x</span><span class="mord">−</span></span></span></span>i * $y;
}

var_dump(fmod(.25, .05)); // float(0.05)
var_dump(fmod_round(.25, .05)); // float(0)
?>

nospam at neonit dot de ¶

8 years ago

Note that fmod does not behave like a similar function written in PHP itself does due to the lack of fixing floating point representation errors.

Have a look at this:
<?php
var_dump(10 / (10 / 3) === 3.0); // bool(true)
var_dump(fmod(10, 10 / 3)); // float(3.3333333333333)
var_dump(fmod(10, 10 / 3) < 10 / 3); // bool(true)
?>

Internally there is no way of exactly representing the result of 10 / 3, so it will always be a bit above or below the actual result. In this case, the example proves it being a bit above the actual result.

PHP seems quite good at auto-fixing floating point representation errors so they behave like the user would expect it. That's why the first line yields true, although the result is slightly below 3 (like 2.9999999999[something]). I failed to trick PHP into rounding or cropping the result to 2.

However, fmod seems to not apply these fixes during calculations. From 10 / 3 it gets a value slightly below 3, floors it to 2 and returns 10 - 2 * 10 / 3, which is slightly less than the actual result of 10 / 3, but looks like 10 / 3 (third line).

Unfortunately, this is not the expected result. See other notes for high quality fixes.

dePijd ¶

15 years ago

This class ran through several unit tests and fixes all failures found in bugs.php.net

<?php
abstract class MyNumber {
    public static function isZero($number, $precision = 0.0000000001)
    {
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi><mi>r</mi><mi>e</mi><mi>c</mi><mi>i</mi><mi>s</mi><mi>i</mi><mi>o</mi><mi>n</mi><mo>=</mo><mi>a</mi><mi>b</mi><mi>s</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">precision = abs(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.854em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">p</span><span class="mord mathnormal">rec</span><span class="mord mathnormal">i</span><span class="mord mathnormal">s</span><span class="mord mathnormal">i</span><span class="mord mathnormal">o</span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">ab</span><span class="mord mathnormal">s</span><span class="mopen">(</span></span></span></span>precision);
        return -$precision < (float)$number && (float)$number < $precision;
    }
    public static function isEqual($number1, $number2)
    {
        return self::isZero($number1 - $number2);
    }
    public static function fmod($number1, $number2)
    {
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi><mi>e</mi><mi>s</mi><mi>t</mi><mo>=</mo><mi>f</mi><mi>m</mi><mi>o</mi><mi>d</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">rest = fmod(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6151em;"></span><span class="mord mathnormal">res</span><span class="mord mathnormal">t</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mord mathnormal">m</span><span class="mord mathnormal">o</span><span class="mord mathnormal">d</span><span class="mopen">(</span></span></span></span>number1, $number2);
        if (self::isEqual($rest, $number2)) {
            return 0.0;
        }
        if (mb_strpos($number1, ".") === false) {
            $decimals1 = 0;
        } else {
            <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>d</mi><mi>e</mi><mi>c</mi><mi>i</mi><mi>m</mi><mi>a</mi><mi>l</mi><mi>s</mi><mn>1</mn><mo>=</mo><mi>m</mi><msub><mi>b</mi><mi>s</mi></msub><mi>t</mi><mi>r</mi><mi>l</mi><mi>e</mi><mi>n</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">decimals1 = mb_strlen(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">d</span><span class="mord mathnormal">ec</span><span class="mord mathnormal">ima</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">s</span><span class="mord">1</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">m</span><span class="mord"><span class="mord mathnormal">b</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">s</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mopen">(</span></span></span></span>number1) - mb_strpos($number1, ".") - 1;
        }
        if (mb_strpos($number2, ".") === false) {
            $decimals2 = 0;
        } else {
            <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>d</mi><mi>e</mi><mi>c</mi><mi>i</mi><mi>m</mi><mi>a</mi><mi>l</mi><mi>s</mi><mn>2</mn><mo>=</mo><mi>m</mi><msub><mi>b</mi><mi>s</mi></msub><mi>t</mi><mi>r</mi><mi>l</mi><mi>e</mi><mi>n</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">decimals2 = mb_strlen(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">d</span><span class="mord mathnormal">ec</span><span class="mord mathnormal">ima</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">s</span><span class="mord">2</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">m</span><span class="mord"><span class="mord mathnormal">b</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">s</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mopen">(</span></span></span></span>number2) - mb_strpos($number2, ".") - 1;
        }
        return (float)round($rest, max($decimals1, $decimals2));
    }
}
?>

cory at lavacube dot net ¶

20 years ago

I don't believe that is correct.

Try this out using your patch:
<?php

echo duration( mktime(0, 0, 0, 1, 0, 2006)-time() );

?>

As of right now, this will read:
1 month, 22 days, 24 hours, 49 minutes, 15 seconds

Which is completely incorrect. Seeing as how it is the 9th of December.

The real real flaw here is how the 'year' and 'month' periods are calculated. As most months vary in length...

Thank you very much SnakeEater251 for pointing this out.

The quickest way to get slightly more accurate results, is to use averages based on one "true" year, which is 365.25 days.

Change the year and month to:
      'year'       => 31557600, // one 'true year' (365.25 days)
      'month'    => 2629800, // one 'true year' divided by 12 :-)

I will work on developing a true fix, for pin-point accuracy. ;-)

 - Cory Christison

alex at xelam dot net ¶

21 years ago

Integer Modulo

If you want the remainder of the division of two Integers rather than Floats, use "%"; eg:

<?php
$a = 4;
$b = 3;

print($a % $b);
?>

Will output "1".

dan danschafer net ¶

7 years ago

WARNING: Due to how floating point numbers work, fmod() and any simple alternatives are problematic when there is either a massive orders of magnitude different between the input <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mi>a</mi><mi>n</mi><mi>d</mi></mrow><annotation encoding="application/x-tex">x and </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">x</span><span class="mord mathnormal">an</span><span class="mord mathnormal">d</span></span></span></span>y, or the input and output values. If you need to work with large numbers or arbitrary precision, it is best to work with something like BC Math or GMP.

When working around fmod()'s problems, remember that floor() always goes towards -INF, not 0. This causes a commonly proposed fmod() alternative to only work with positive numbers:
<?php 
function fmod_positive_only($x, $y) {
    return <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>−</mo><mi>f</mi><mi>l</mi><mi>o</mi><mi>o</mi><mi>r</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">x - floor(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6667em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">x</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">−</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal" style="margin-right:0.02778em;">oor</span><span class="mopen">(</span></span></span></span>x/$y) * $y;
}
?>
Given these simplistic input values:
fmod_positive_only(-5, 3) = 1 (wrong)
-5 % 3 = -2 (correct)

Correctly removing the decimal part of the quotient can be achieved with either casting to an int (always goes towards zero) or dynamically choosing ceil() or floor(). Dynamically choosing floor or ceil in an attempt to keep precision is overkill. If your <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mi>a</mi><mi>n</mi><mi>d</mi></mrow><annotation encoding="application/x-tex">x and </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal">x</span><span class="mord mathnormal">an</span><span class="mord mathnormal">d</span></span></span></span>y values are so different that it suffers from an overflow problem when casting, it was probably going to have precision problems anyway (see warnings below).

<?php 
function fmod_overkill($x, $y) {
    if (!$y) { return NAN; }
    <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>q</mi><mo>=</mo></mrow><annotation encoding="application/x-tex">q = </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.1944em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>x / $y;
    <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>f</mi><mo>=</mo><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">f = (</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mopen">(</span></span></span></span>q < 0 ? 'ceil' : 'floor');
    return <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>−</mo></mrow><annotation encoding="application/x-tex">x - </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6667em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">x</span><span class="mord">−</span></span></span></span>f($q) * $y;
}
?>

This is the "best" alternative for fmod() when given "normal" numbers.
<?php
function fmod_alt($x, $y) {
    if (!$y) { return NAN; }
    return floatval($x - intval($x / <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mo stretchy="false">)</mo><mo>∗</mo></mrow><annotation encoding="application/x-tex">y) * </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mclose">)</span><span class="mord">∗</span></span></span></span>y);
}
?>

WARNING: Even when you get a non-zero response, know your input numbers and when fmod() can go wrong. For large values or depending on your input variable types, float still may not contain enough precision to get back the correct answer. Here are a few problems with fmod() and their alternatives.

PHP_INT_MAX = 9223372036854775807
fmod(PHP_INT_MAX, 2) = 0 (wrong)
fmod_alt(PHP_INT_MAX, 2) = 0 (wrong)
PHP_INT_MAX % 2 = 1 (correct)

fmod(PHP_INT_MAX, PHP_INT_MAX - 1) = 0 (wrong)
fmod_alt(PHP_INT_MAX, PHP_INT_MAX - 1) = 1 (correct)
fmod_alt(PHP_INT_MAX, PHP_INT_MAX - 1.0) = 0 (wrong)
PHP_INT_MAX % (PHP_INT_MAX - 1) = 1 (correct)
PHP_INT_MAX % (PHP_INT_MAX - 1.0) = 9223372036854775807 (wrong)

fmod(PHP_INT_MAX, 131) =  98 (wrong)
fmod_alt(PHP_INT_MAX, 131) = 359 (wrong)
fmod_positive_only(PHP_INT_MAX, 131) = 0 (wrong)
PHP_INT_MAX % 131 = 97 (correct)

picaune at hotmail dot com ¶

22 years ago