floor

    (PHP 4, PHP 5, PHP 7, PHP 8)

    floor — Round fractions down

    Description

    floor(int|float $num): float

    Returns the next lowest integer value (as float) by rounding down num if necessary.

    Parameters

    num

    The numeric value to round

    Return Values

    num rounded to the next lowest integer. The return value of floor() is still of type float.

    Changelog

    Version Description
    8.0.0 num no longer accepts internal objects which support numeric conversion.

    Examples

    Example #1 floor() example

    <?php
    echo floor(4.3); // 4
    echo floor(9.999); // 9
    echo floor(-3.14); // -4
    ?>

    See Also

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    User Contributed Notes 12 notes

    up
    49
    greene dot mc at removethispart dot gmail dot com
    16 years ago
    I believe this behavior of the floor function was intended. Note that it says "the next lowest integer". -1 is "higher" than -1.6. As in, -1 is logically greater than -1.6. To go lower the floor function would go to -2 which is logically less than -1.6.

    Floor isn't trying to give you the number closest to zero, it's giving you the lowest bounding integer of a float.

    In reply to Glen who commented:
    Glen
    01-Dec-2007 04:22
    <?php
    echo floor(1.6); // will output "1"
    echo floor(-1.6); // will output "-2"
    ?>

    instead use intval (seems to work v5.1.6):

    <?php
    echo intval(1.6); // will output "1"
    echo intval(-1.6); // will output "-1"
    ?>
    up
    40
    seppili_ at gmx dot de
    14 years ago
    I use this function to floor with decimals:
    <?php

    function floordec($zahl,$decimals=2){
    return     floor($zahl*pow(10,$decimals))/pow(10,$decimals);
    }
    ?>
    up
    16
    Antonio
    5 years ago
    <?php
    echo (2.3 * 100) . ' - ' . round(2.3 * 100, 0) . ' - ' . floor(2.3 * 100);
    ?>.

    Result:
    230 - 230 - 229

    Be careful!
    up
    11
    maikl
    10 years ago
    A correction to the funcion floor_dec from the user "php is the best".
    If the number is 0.05999 it returns 0.59 because the zero at left position is deleted.
    I just added a '1' and after the floor or ceil call remove with a substr.
    Hope it helps.

    function floor_dec($number,$precision = 2,$separator = '.') {
    $numberpart=explode($separator,$number);
    $numberpart[1]=substr_replace($numberpart[1],$separator,$precision,0);
    if($numberpart[0]>=0) {
    $numberpart[1]=substr(floor('1'.$numberpart[1]),1);
    } else {
    $numberpart[1]=substr(ceil('1'.$numberpart[1]),1);
    }
    $ceil_number= array($numberpart[0],$numberpart[1]);
    return implode($separator,$ceil_number);
    }
    up
    16
    benrr101 at gmail dot com
    16 years ago
    But, if you want the number closest to zero, you could use this:
    <?php
    if($foo > 0) {
    floor($foo);
    } else {
    ceil($foo);
    }
    ?>

    -benrr101
    up
    12
    fragov at gmail dot com
    15 years ago
    Have solved a "price problem":

    <?php
    $peny     = floor($row->price*1000) - floor($row->price)*1000)/10;
    ?>
    up
    5
    Leon Grdic
    8 years ago
    Warning: do not use Seppili's function to floor with decimals. It will lead you to a lot of trouble because of float number precision.

    For example floordec(0.29, 2) will result in 0.28.

    Here's a little fix that will help you get around some problems:

    <?php
    function floordec($value,$decimals=2){
    return     floor($value*pow(10,$decimals)+0.5)/pow(10,$decimals);
    }
    ?>
    up
    10
    jay at w3prodigy dot com
    16 years ago
    Note:

    <?php
    $int     = 0.99999999999999999;
    echo     floor($int); // returns 1
    ?>

    and

    <?php
    $int     = 0.9999999999999999;
    echo     floor($int); // returns 0
    ?>
    up
    7
    jolyon at mways dot co dot uk
    20 years ago
    Beware of FLOAT weirdness!

    Floats have a mind of their own, and what may look like an integer stored in a float isn't.

    Here's a baffling example of how floor can be tripped up by this:

    <?php
    $price     = 79.99;

    print     $price."\r\n"; // correct result, 79.99 shown

    $price = $price * 100;

    print     $price."\r\n"; // correct result, 7999 shown

    print floor($price); // 7998 shown! what's going on?
    ?>

    The thing to remember here is that the way a float stores a value makes it very easy for these kind of things to happen. When the 79.99 was multiplied by 100, the actual value stored in the float was probably something like 7998.9999999999999999999999999999999999, PHP would print out 7999 when the value is displayed but floor would therefore round this down to 7998.

    THe moral of this story - never use float for anything that needs to be accurate! If you're doing prices for products or a shopping cart, then always use an integer and store prices as a number of pence, you'll thank me for this later :)
    up
    3
    Glen
    16 years ago
    <?php
    echo floor(1.6); // will output "1"
    echo floor(-1.6); // will output "-2"
    ?>

    instead use intval (seems to work v5.1.6):

    <?php
    echo intval(1.6); // will output "1"
    echo intval(-1.6); // will output "-1"
    ?>
    up
    -1
    Anonymous
    22 years ago
    mathematical functions lack a floating point version of the modulo operation, which returns the difference between the floor() of the argument and the argument itself:

    <?php
    function fmod($value) {
    return     $value - floor($value);
    }
    ?>

    Very useful with trigonometric functions to reduce the angle argument to a circle that includes angle 0.

    Useful also to reduce an arbitrarily large floating point value into an entropy source, by first transforming this value into a pair using logarithm functions with distinct bases (add 1 if the function can return 0, to avoid floating point errors with logarithms!):

    <?php
    $f     = 1 + @disk_free_space("/tmp");
    $r = (int)(fmod(Log($f)) * 0x7FFFFFFF)
    ^ (int)(    fmod(Log10($f)) * 0x7FFFFFFF)
    ?>

    Then $r can be used as a good entropy source, if the free space in your temporary folder used by PHP is constantly evolving within a large range of values.

    You can combine this value by xoring it with other values such as time(), (int)microtime(), ip2long($_SERVER['REMOTE_ADDR'], $_SERVER['REMOTE_PORT'], getmypid(), ...
    up
    -5
    lewis at lewishenshall dot co dot uk
    15 years ago
    If you're wanting to round down to the nearest hundred:

    <?php
    function rounddowntohundred($theNumber) {
    if (    strlen($theNumber)<3) {
    $theNumber=$theNumber;
    } else {
    $theNumber=substr($theNumber, 0, strlen($theNumber)-2) . "00";

    }
    return     $theNumber;

    }
    ?>
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