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floor — Abrunden
Liefert die nächste ganze Zahl, die kleiner oder gleich dem Parameter value ist.
Der abzurundende Wert
Liefert den abgerundeten Wert zurück. Dieser ist nach wie vor vom Typ float und nicht vom Typ integer wegen des größeren Wertebereichs von float.
Beispiel #1 floor() Beispiel
<?php
echo floor(4.3); // 4
echo floor(9.999); // 9
echo floor(-3.14); // -4
?>
Another quick way to round down to the nearest 100 (including 0):
<?php
function floor100($num) {
return (floor($num / 100) * 100);
}
?>
I use this function to floor with decimals:
<?php
function floordec($zahl,$decimals=2){
return floor($zahl*pow(10,$decimals))/pow(10,$decimals);
}
?>
Here's a shorter versiion of "round to nearest hundred"
<?php
function rd100($num)
{
return round($num / 100) * 100;
}
?>
If you're wanting to round down to the nearest hundred:
<?php
function rounddowntohundred($theNumber) {
if (strlen($theNumber)<3) {
$theNumber=$theNumber;
} else {
$theNumber=substr($theNumber, 0, strlen($theNumber)-2) . "00";
}
return $theNumber;
}
?>
Have solved a "price problem":
<?php
$peny = floor($row->price*1000) - floor($row->price)*1000)/10;
?>
marc at moblaster's rounding technique for handling financial truncation fails for 0.0, and probably has unintended consequences for values less than 0. Something like this should do the trick:
function truncateMoneyFloat($amount)
{
if ($amount > 0.005) return round($amount - 0.005,2);
elseif ($amount < -0.005) return round($amount + 0.005,2);
else return 0.0;
}
However, +1 billion for jolyon at mways' comment regarding abandoning floats entirely when processing financial data. Create a money class and track the value internally with an integer. Provide methods to scale by float values where the rounding behavior can be controlled by an explicit policy variable.
But, if you want the number closest to zero, you could use this:
<?php
if($foo > 0) {
floor($foo);
} else {
ceil($foo);
}
?>
-benrr101
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"
?>
Note:
$int = 0.99999999999999999;
echo floor($int); // returns 1
and
$int = 0.9999999999999999;
echo floor($int); // returns 0
There is actually a much easier and simpler way to chop off any fraction of a penny in financial calculations. Here is the code:
function round_down_to_penny( $p ) {
$p=round($p-0.005,2);
return $p;
}
In other words, just subtract 0.005 and round that to 2 decimal places.
You can easily verify that any price from say 7.21 to 7.2199999 ends up as 7.21.
<?php
echo floor(1.6); // will output "1"
echo floor(-1.6); // will output "-2"
?>
instead use intval (seems to work v5.1.6):
<?php
echo intval(1.6); // will output "1"
echo intval(-1.6); // will output "-1"
?>
How about something like this:
function goodFloor($x) {
return floor(round($x, strlen((string)($x))));
}
It's not elegant but at least short...
Regards,
Wojciech
Good catch Matthäus.
After thinking about it a bit more, it seems there isn't an elegant solution. The only way to properly handle it is to do some string manipulation, chop it to a specific decimal length, potentially string pad it, then do your rounding and floor.
As a response to Jared Fine:
There is a little problem with your suggestion.
floor(2.95) == 2 != floor(round(2.95, 1)) == 3
as round(2.95, 1) == 3.0
Due to the floating point precision issue (http://www.php.net/float) if you round() one additional decimal point prior to calling floor() you will get the expected result.
For example:
echo floor((0.1 + 0.7) * 10); // echo's 7
echo floor(round((0.1 + 0.7) * 10, 1)); // echo's 8
Simpler version of Bruteork's example (though not making use of floor()):
<?php
if ($counter % 2 == 0) echo "even";
?>
If you are after just removing the decimal places and returning an integer, try:
<?
$iPosDecimalNo = 5.67;
$iNegDecimalNo = -5.67;
print (int)$iPosDecimalNo;
print (int)$iNegDecimalNo;
?>
result will:
5
-5
No rounding up or down, just truncation and works for positive and negative numbers.
Here's a way to get around jolyon's 79.99 problem (below). If you want to take a float value representing a price and drop off any fractions of a cent, use this:
<?php
function round_to_penny($amount){
$string = (string)($amount * 100);
$string_array = split("\.", $string);
$int = (int)$string_array[0];
$return = $int / 100;
return $return;
}
print( round_to_penny(79.99999) ); //result: 79.99
?>
Probably not super efficient, but get's the job done if you've already invested in using float values.
Cheers,
Sam
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:
<?
$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 :)
For calculating the number of days, hours, minutes and seconds to an event.
<?
$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";
?>
In response to PHP Helper, the floor function does strip the decimal part if the number is positive. However, if the number is negative, it will not. for example:
<?php
$test = 5.6;
echo floor($test); //5
$test = -5.6;
echo floor($test); //-6
?>
The rounding mentioned in PHP Helper's post will work for both positive and negative numbers.
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 "$length";
?>
Result: 5.123
Just a quick example of how to use this method
The first is just used to determine whether a number is even or odd:
<?
if(($x - (2 * floor($x/2))) == 0) echo "even";
else echo "odd";
?>
The second is just to determine a person’s age by comparing their birthday with the current date and rounding down:
<? $age = floor((date(Ymd) - $bday)/10000); ?>
mathematical functions lack a floating point version of the modulo operation, which returns the difference between the floor() of the argument and the argument itself:
function fmod($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!):
$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(), ...
In response to netben's comment, another conversion for a string is:
$myStr = "29.01";
$myStr = (float) $myStr;
In all, any string (as used as in this example) will be treated as float, and no conversion necessary.
//Using floor() to round decimals.
$original_price=12.72
$discount=$original_price*.40;
$discount=floor(($discount * 100)+.5)/100;
//$discount=5.088
//$discount after floor() = 5.09
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