floor

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

floor — 端数の切り捨て

説明

floor(int|float $num): float

必要に応じて num を丸めることにより、 num をこえない最大の整数の値を (float 型で) 返します。

パラメータ

num: 丸める数値。

戻り値

num をこえない最大の整数の値を返します。 floor() の戻り値は float 型のままとなります。

変更履歴

バージョン	説明
8.0.0	`num` は、数値への変換をサポートした内部オブジェクトを受け入れなくなりました。

例

例1 floor() の例

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

参考

ceil() - 端数の切り上げ
round() - 浮動小数点数を丸める

Improve This Page

Learn How To Improve This Page • Submit a Pull Request • Report a Bug

＋add a note

User Contributed Notes 12 notes

down

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"
?>

down

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);
}
?>

down

Antonio ¶

5 years ago

<?php
echo (2.3 * 100) . ' - ' . round(2.3 * 100, 0) .  ' - ' . floor(2.3 * 100);
?>.

Result:
230 - 230 - 229

Be careful!

down

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);
}

down

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

down

fragov at gmail dot com ¶

15 years ago

Have solved a "price problem":



<?php

$peny = floor($row->price*1000) - floor($row->price)*1000)/10;

?>

down

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);
}
?>

down

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

?>

down

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 :)

down

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"
?>

down

-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(), ...

down

-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;

}
?>

＋add a note