expm1
The better way to round up/down to the nearest hundred (or thousand, etc.) is with roundBetter():
<?php
// This function is backwards compatible with round(),
// but provides an optional extra argument which,
// if set and not null, allows you to override the default
// rounding direction. See examples below.
function roundBetter($number, $precision = 0, $mode = PHP_ROUND_HALF_UP, $direction = NULL) {
if (!isset($direction) || is_null($direction)) {
return round($number, $precision, $mode);
}
else {
$factor = pow(10, -1 * $precision);
return strtolower(substr($direction, 0, 1)) == 'd'
? floor($number / $factor) * $factor
: ceil($number / $factor) * $factor;
}
}
// roundBetterUp(1999, -3) => 2000
// roundBetterUp(1001, -3) => 2000
function roundBetterUp($number, $precision = 0, $mode = PHP_ROUND_HALF_UP) {
return roundBetter($number, $precision, $mode, 'up');
}
// roundBetterDown(1999, -3) => 1000
// roundBetterDown(1001, -3) => 1000
function roundBetterDown($number, $precision = 0, $mode = PHP_ROUND_HALF_UP) {
return roundBetter($number, $precision, $mode, 'down');
}
?>
floor
(PHP 4, PHP 5)
floor — Round fractions down
Description
float floor
( float $value
)
Returns the next lowest integer value by rounding down value if necessary.
Parameters
- value
-
The numeric value to round
Return Values
value rounded to the next lowest integer. The return value of floor() is still of type float because the value range of float is usually bigger than that of integer.
Examples
Example #1 floor() example
<?php
echo floor(4.3); // 4
echo floor(9.999); // 9
echo floor(-3.14); // -4
?>
add a note
User Contributed Notes
floor
dr+php at dakotaryan dot com
21-Sep-2011 05:22
seppili_ at gmx dot de
05-Mar-2010 01:52
I use this function to floor with decimals:
<?php
function floordec($zahl,$decimals=2){
return floor($zahl*pow(10,$decimals))/pow(10,$decimals);
}
?>
lewis at lewishenshall dot co dot uk
25-Feb-2009 04:12
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;
}
?>
fragov at gmail dot com
14-Jan-2009 02:39
Have solved a "price problem":
<?php
$peny = floor($row->price*1000) - floor($row->price)*1000)/10;
?>
benrr101 at gmail dot com
11-Jun-2008 03:39
But, if you want the number closest to zero, you could use this:
<?php
if($foo > 0) {
floor($foo);
} else {
ceil($foo);
}
?>
-benrr101
greene dot mc at removethispart dot gmail dot com
27-May-2008 07:08
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"
?>
jay at w3prodigy dot com
25-Mar-2008 06:01
Note:
<?php
$int = 0.99999999999999999;
echo floor($int); // returns 1
?>
and
<?php
$int = 0.9999999999999999;
echo floor($int); // returns 0
?>
Glen
30-Nov-2007 06:22
<?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"
?>
jolyon at mways dot co dot uk
10-Aug-2004 03:41
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 :)
illyena at musefish dot net
12-May-2004 09:53
For calculating the number of days, hours, minutes and seconds to an event.
<?php
$then = date(mktime(8,0,0,6,25,2004)); //remember that mktime is hour,min,sec,month,day,year
$now = date("U"); // "U" is the number of seconds since the epoch, equivilant to using "YmdHis"
$time = $then - $now; //gets the number of seconds between now and the event
$days = floor($time/86400); //rounds down to the whole number, in this case # of days
echo $days." Days";
$time = $time - ($days*86400); //leaves you with the amount of time ramaining after subtracting the days
$hours = floor($time/3600); //rounds down to the whole number, in this case # of hours
echo $hours." Hours";
$time = $time - ($hours*3600); //leaves you with the amount of time ramaining after subtracting the hours
$min = floor($time/60); //rounds down to the whole number, in this case # of minutes
echo $min." Minutes";
$sec = $time - ($min*60); //leaves you with the amount of time ramaining after subtracting the minutes which is equivilant to the remainins seconds
echo $sec." Seconds";
?>
PHP Helper
19-Dec-2003 07:39
floor basically truncates, or chops off everything to the right of a decimal. For instance, if you have a length of 5.1234, but just wanted the whole number, you could use the following code:
<?php
$length = 5.1234; //this is our original length
$length = floor($length); //length is truncated, original variable name is kept
print "$length"; //this prints our result
?>
This code would print the following: 5
Now, although there is a specific function in PHP for rounding, rounding can also be performed with the floor function. Let's say we wanted to round the length to the hundredths place.
<?php
$length = 5.1234;
$length = floor(($length) * 100 + .5) * .01;
print "$length";
?>
The result is: 5.12
This works because, first, the length is multiplied by 100, which moves the decimal point to the right two places, giving us the value of 512.34. Next .5 is added to the length, which gives us a value of 512.84. Then the floor function truncates the value, leaving us with 512. Lastly, to compensate for multiplying by 100 earlier, now we must divide by 100, or in this case, multiply by .01. This moves the decimal point back 2 places to it's original place and gives us the rounded value of 5.12.
We can also round to other values, such as the thousandths, by adjusting the code as follows:
<?php
$length = 5.1234;
$length = floor(($length) * 1000 + .5) * .001;
print "$length";
?>
Result: 5.123
09-Sep-2002 09:08
mathematical functions lack a floating point version of the modulo operation, which returns the difference between the floor() of the argument and the argument itself:
<?php
function fmod($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(), ...