PHP 5.5.17 is available

浮動小数点数

浮動小数点数 (あるいは "float", "double", "実数") は、次の構文により指定できます。

<?php
$a 
1.234
$b 1.2e3
$c 7E-10;
?>

規約:

LNUM          [0-9]+
DNUM          ([0-9]*[\.]{LNUM}) | ({LNUM}[\.][0-9]*)
EXPONENT_DNUM [+-]?(({LNUM} | {DNUM}) [eE][+-]? {LNUM})

float の大きさはプラットフォーム依存です。ただし、通常はおよそ 10 進数で 14 桁の精度があり、最大値は ~1.8e308 (これは 64ビット IEEE フォーマットです) となります。

警告

浮動小数点数の精度

浮動小数点数の精度は有限です。 システムに依存しますが、PHP は通常 IEEE 754 倍精度フォーマットを使います。 この形式は、1.11e-16 のオーダーでの丸め処理で誤差が発生します。 複雑な算術演算をすると、誤差はさらに大きくなるでしょう。そしてもちろん、 いくつかの演算を組み合わせる場合にも誤差を考慮しなければなりません。

さらに、十進数では正確な小数で表せる有理数、たとえば 0.10.7 は、 二進数の浮動小数点数としては正確に表現できません。 これは、仮数部をいくら大きくしても同じです。 したがって、それを内部的な二進数表現に変換する際には、どうしても多少精度が落ちてしまいます。 その結果、不思議な結果を引き起こすことがあります。たとえば、 floor((0.1+0.7)*10) の結果はたいてい 7 となるでしょう。おそらくは 8 を想定していらっしゃるでしょうが、そのようにはなりません。 これは、(この計算結果の) 内部的な値が 7.9999999999999991118... のようになっているからです。

よって、小数の最後の桁を信用してはいけませんし、 小数を直接比較して等しいかどうかを調べてはいけません。より高い精度が必要な場合には、 任意精度数学関数または gmp 関数を代わりに使用してください。

もっと「シンプルな」説明が欲しければ、» floating point guide を見るといいでしょう。"Why don’t my numbers add up? (なんで数字が足されないの?)" というタイトルが付いています。

float への変換

文字列型がどのようにして浮動小数点数に変換されるかに関する詳細な情報は、 文字列の数値型への変換 のセクションをご覧ください。 そのほかの型の浮動小数点数への変換については、整数型への変換と同様です。 詳細は整数型への変換 のセクションをご覧ください。 PHP 5 以降、オブジェクトを浮動小数点数に変換しようとした場合には、 通知がスローされます。

float の比較

先ほど警告したように、浮動小数点数値が等しいかどうかを比較するのには問題があります。 これは、浮動小数点数値の内部表現形式に起因するものです。 しかし、この制限を回避して浮動小数点数値の値を比較する方法もあります。

浮動小数点数値が等しいかどうかを調べるには、比較時の丸め誤差の上界を用います。 この値は計算機イプシロンあるいは丸め単位と呼ばれ、 計算時に扱える最小の差分を表します。

$a$b は、精度 5 桁では等しくなります。

<?php
$a 
1.23456789;
$b 1.23456780;
$epsilon 0.00001;

if(
abs($a-$b) < $epsilon) {
    echo 
"true";
}
?>

NaN

数値演算の結果が、定数 NAN で表される値になることがあります。 この定数は、浮動小数点演算における未定義の値あるいは表現不能な値を表します。 この値を他の値と比較した場合、たとえ自分自身との比較であっても結果は FALSE になります。 緩やかな比較の場合も厳格な比較の場合の同様です。

NAN はさまざまな値の数を表すものなので、 NAN を他の値を比較してはいけません。たとえ自分自身とであってもです。 チェックをする場合には、かわりに is_nan() を使います。

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User Contributed Notes 29 notes

up
16
www.sarioz.com
11 years ago
just a comment on something the "Floating point precision" inset, which goes: "This is related to .... 0.3333333."

While the author probably knows what they are talking about, this loss of precision has nothing to do with decimal notation, it has to do with representation as a floating-point binary in a finite register, such as while 0.8 terminates in decimal, it is the repeating 0.110011001100... in binary, which is truncated.  0.1 and 0.7 are also non-terminating in binary, so they are also truncated, and the sum of these truncated numbers does not add up to the truncated binary representation of 0.8 (which is why (floor)(0.8*10) yields a different, more intuitive, result).  However, since 2 is a factor of 10, any number that terminates in binary also terminates in decimal.
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7
catalin dot luntraru at gmail dot com
10 months ago
$x = 8 - 6.4;  // which is equal to 1.6
$y = 1.6;
var_dump($x == $y); // is not true

PHP thinks that 1.6 (coming from a difference) is not equal to 1.6. To make it work, use round()

var_dump(round($x, 2) == round($y, 2)); // this is true

This happens probably because $x is not really 1.6, but 1.599999.. and var_dump shows it to you as being 1.6.
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12
magicaltux at php dot net
4 years ago
In some cases you may want to get the maximum value for a float without getting "INF".

var_dump(1.8e308); will usually show: float(INF)

I wrote a tiny function that will iterate in order to find the biggest non-infinite float value. It comes with a configurable multiplicator and affine values so you can share more CPU to get a more accurate estimate.

I haven't seen better values with more affine, but well, the possibility is here so if you really thing it's worth the cpu time, just try to affine more.

Best results seems to be with mul=2/affine=1. You can play with the values and see what you get. The good thing is this method will work on any system.

<?php
 
function float_max($mul = 2, $affine = 1) {
   
$max = 1; $omax = 0;
    while((string)
$max != 'INF') { $omax = $max; $max *= $mul; }

    for(
$i = 0; $i < $affine; $i++) {
     
$pmax = 1; $max = $omax;
      while((string)
$max != 'INF') {
       
$omax = $max;
       
$max += $pmax;
       
$pmax *= $mul;
      }
    }
    return
$omax;
  }
?>
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7
zelko at mojeime dot com
3 years ago
<?php
   $binarydata32
= pack('H*','00000000');
  
$float32 = unpack("f", $binarydata32); // 0.0

  
$binarydata64 = pack('H*','0000000000000000');
  
$float64 = unpack("d", $binarydata64); // 0.0
?>

I get 0 both for 32-bit and 64-bit numbers.

But, please don't use your own "functions" to "convert" from float to binary and vice versa. Looping performance in PHP is horrible. Using pack/unpack you use processor's encoding, which is always correct. In C++ you can access the same 32/64 data as either float/double or 32/64 bit integer. No "conversions".

To get binary encoding:
<?php
   $float32
= pack("f", 5300231);
  
$binarydata32 =unpack('H*',$float32); //"0EC0A14A"

  
$float64 = pack("d", 5300231);
  
$binarydata64 =unpack('H*',$float64); //"000000C001385441"
?>

And my example from half a year ago:
<?php
    $binarydata32
= pack('H*','0EC0A14A');
   
$float32 = unpack("f", $binarydata32); // 5300231
  
   
$binarydata64 = pack('H*','000000C001385441');
   
$float64 = unpack("d", $binarydata64); // 5300231
?>

And please mind the Big and Little endian boys...
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6
rick at ninjafoo dot com
9 years ago
Concider the following:

(19.6*100) != 1960 

echo gettype(19.6*100) returns 'double', However even .....

(19.6*100) !== (double)1960

19.6*100 cannot be compaired to anything without manually
casting it as something else first.

(string)(19.6*100) == 1960

Rule of thumb, if it has a decimal point, use the BCMath functions.
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6
Julian L
3 years ago
Convert a hex string into a 32-bit IEEE 754 float number.  This function is 2 times faster then the below hex to 32bit function.  This function only changes datatypes (string to int) once. Also, this function is a port from the hex to 64bit function from below.

<?php
function hexTo32Float($strHex) {
   
$v = hexdec($strHex);
   
$x = ($v & ((1 << 23) - 1)) + (1 << 23) * ($v >> 31 | 1);
   
$exp = ($v >> 23 & 0xFF) - 127;
    return
$x * pow(2, $exp - 23);
}
?>

<?php
//example
echo hexTo32Float("C4028000"); // outputs: -522
echo hexTo32Float("457F9000"); // outputs: 4089
echo hexTo32Float("2D7F5");    // outputs: 6.00804264307E-39
echo hexTo32Float("0002D7F5"); // outputs: 6.00804264307E-39
echo hexTo32Float("47D9F95E"); // outputs: 111602.734375
?>
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4
davidszilardd at gmail dot com
2 years ago
The function returns 5 for 5,000 because if there is no decimal point, then the first strpos will be FALSE, and FALSE < 1 is TRUE so the condition will be still true.

It should be checked whether strpos returns a valid position:

<?php
function str2num($str)
{
      if (
strpos($str, '.') !== FALSE && strpos($str,    ',') !== FALSE && strpos($str, '.') < strpos($str,','))
          {
           
$str = str_replace('.','',$str);
           
$str = strtr($str,',','.');           
        }
        else
        {
           
$str = str_replace(',','',$str);           
        }
       
        return (float)
$str;
}
?>
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5
jack at surfacefinishtech dot com
1 year ago
<?php
/** hex2float
* (Convert 8 digit hexadecimal value to float (single-precision 32bits)
* Accepts 8 digit hexadecimal values in a string
* @usage:
* hex2float32n("429241f0"); returns -> "73.128784179688"
* */
function hex2float($number) {
   
$binfinal = sprintf("%032b",hexdec($number));
   
$sign = substr($binfinal, 0, 1);
   
$exp = substr($binfinal, 1, 8);
   
$mantissa = "1".substr($binfinal, 9);
   
$mantissa = str_split($mantissa);
   
$exp = bindec($exp)-127;
   
$significand=0;
    for (
$i = 0; $i < 24; $i++) {
       
$significand += (1 / pow(2,$i))*$mantissa[$i];
    }
    return
$significand * pow(2,$exp) * ($sign*-2+1);
}
?>
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5
backov at spotbrokers-nospamplz dot com
11 years ago
I'd like to point out a "feature" of PHP's floating point support that isn't made clear anywhere here, and was driving me insane.

This test (where var_dump says that $a=0.1 and $b=0.1)

if ($a>=$b) echo "blah!";

Will fail in some cases due to hidden precision (standard C problem, that PHP docs make no mention of, so I assumed they had gotten rid of it). I should point out that I originally thought this was an issue with the floats being stored as strings, so I forced them to be floats and they still didn't get evaluated properly (probably 2 different problems there).

To fix, I had to do this horrible kludge (the equivelant of anyway):

if (round($a,3)>=round($b,3)) echo "blah!";

THIS works. Obviously even though var_dump says the variables are identical, and they SHOULD BE identical (started at 0.01 and added 0.001 repeatedly), they're not. There's some hidden precision there that was making me tear my hair out. Perhaps this should be added to the documentation?
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4
Bob
5 years ago
In MySQL, many floating point number types can have a range specified using 2 values, the "precision" and the "scale" E.g. 'float(precision,scale)' for the datatype. This syntax means a number may be <precision> bits long, but may only have <scale> bits after the decimal point. E.g. a 'float(5,2)' field may have the values -999.99 to 999.99.
Here is a function to validate a PHP float using this syntax:
<?php
function validate_float($float, $precision, $scale)
{
   
$max = (float)str_pad("", $precision-$scale, '9').'.'.str_pad("", $scale, '9');
   
$min = (float)"-$max";

    if((
$float < $min) || ($float > $max)) return false;
    else return
true;
}
?>
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4
feline at NOSPAM dot penguin dot servehttp dot com
10 years ago
General computing hint: If you're keeping track of money, do yourself and your users the favor of handling everything internally in cents and do as much math as you can in integers. Store values in cents if at all possible. Add and subtract in cents. At every operation that wii involve floats, ask yourself "what will happen in the real world if I get a fraction of a cent here" and if the answer is that this operation will generate a transaction in integer cents, do not try to carry fictional fractional accuracy that will only screw things up later.
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2
kjohnson at zootweb dot com
6 years ago
PHP switches from the standard decimal notation to exponential notation for certain "special" floats. You can see a partial list of such "special" values with this:

<?php
for( $tmp = 0, $i = 0; $i < 100; $i++ ) {
   
$tmp += 100000;
    echo
round($tmp),"\n";
}
?>

So, if you add two floats, end up with a "special" value, e.g. 1.2E+6, then put that value unmodified into an update query to store the value in a decimal column, say, you will likely get a failed transaction, since the database will see "1.2E+6" as varchar data, not decimal. Likewise, you will likely get an XSD validation error if you put the value into xml.

I have to be honest: this is one of the strangest things I have seen in any language in over 20 years of coding, and it is a colossal pain to work around.
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2
Anonymous
4 years ago
Calculations involving float types become inaccurate when it deals with numbers with more than approximately 8 digits long where ever the decimal point is.  This is because of how 32bit floats are commonly stored in memory.  This means if you rely on float types while working with tiny fractions or large numbers, your calculations can end up between tiny fractions to several trillion off.

This usually won't matter when converting to binary memory storage form and editing many applications' float memory addresses directly, or dealing with smaller length numbers.  But if you're working with larger scale numbers and decimals, it's best to switch to working with other types: http://www.php.net/manual/en/refs.math.php
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2
m dot lebkowski+php at gmail dot com
6 years ago
Just another note about the locales. Consider the following code:

<?php
   
// in polish locale decimal separator is ","
   
setlocale(LC_ALL, "pl_PL");
   
$a = 5/2;
    echo (float)(string)
$a;
   
/// prints "2", so the decimal part is dropped
?>

This causes very serious problems in my opinion. In some locale combination the typecasting can be destructive.
Maybe when locale decimal separator is ",", then (float)"2,5" should be recognized as "two and a half"?
Anyway - bare that in mind and be very careful when casting floats to strings and back.
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2
Luzian
8 years ago
Be careful when using float values in strings that are used as code later, for example when generating JavaScript code or SQL statements. The float is actually formatted according to the browser's locale setting, which means that "0.23" will result in "0,23". Imagine something like this:

$x = 0.23;
$js = "var foo = doBar($x);";
print $js;

This would result in a different result for users with some locales. On most systems, this would print:

var foo = doBar(0.23);

but when for example a user from Germany arrives, it would be different:

var foo = doBar(0,23);

which is obviously a different call to the function. JavaScript won't state an error, additional arguments are discarded without notice, but the function doBar(a) would get 0 as parameter. Similar problems could arise anywhere else (SQL, any string used as code somewhere else). The problem persists, if you use the "." operator instead of evaluating the variable in the string.

So if you REALLY need to be sure to have the string correctly formatted, use number_format() to do it!
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2
dev at maintainfit dot com
11 years ago
I was programming an accounting application in MySql that required me to sum a collection of floats and ensure that they equal zero before commiting a transaction, but as seen above a sum of floats cannot always be trusted (as was my case).  I kept getting a very small remainder (like 1.4512431231e-14).  Since I had used number_format(num,2) to set the precision of the numbers in the database to only two (2) decimal places, when the time comes to calculate the sum I simply multiply every number by ten (10), therby eliminating and decimal places and leaving me with integers to preform my sum.  This worked great.
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1
helly at php dot net
6 years ago
Floating point values have a limited precision. Hence a value might not have the same string representation after any processing. That also includes writing a floating point value in your script and directly printing it without any mathematical operations.

If you would like to know more about "floats" and what IEEE 754 is read this: http://docs.sun.com/source/806-3568/ncg_goldberg.html
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1
james dot cridland at virginradio dot co dot uk
11 years ago
The 'floating point precision' box in practice means:

<? echo (69.1-floor(69.1)); ?>
Think this'll return 0.1?
It doesn't - it returns 0.099999999999994

<? echo round((69.1-floor(69.1))); ?>
This returns 0.1 and is the workaround we use.

Note that
<? echo (4.1-floor(4.1)); ?>
*does* return 0.1 - so if you, like us, test this with low numbers, you won't, like us, understand why all of a sudden your script stops working, until you spend a lot of time, like us, debugging it.

So, that's all lovely then.
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0
zelko at mojeime dot com
4 years ago
The was talk about "converting" 32 and 64 bit IEEE754 binary numbers to PHP float. The issue isn't as much converting, since they are already in binary form, as it is casting. PHP doesn't allow direct accessing of memory, but you can still get around a bit.

The right was to read floats (32 and 64 bit) is this:

<?php
    $binarydata32
= pack('H*','0EC0A14A');
   
$float32 = unpack("f", $binarydata32);
   
   
$binarydata64 = pack('H*','000000C001385441');
   
$float64 = unpack("d", $binarydata64);
   
   
var_dump($float32,$float64,$float32==$float64);  
?>

The result of dump():
<?php
array(1) {
  [
1]=>
 
float(5300231)
}
array(
1) {
  [
1]=>
 
float(5300231)
}
bool(true)
?>

Note: mind the Big and Little endian boys
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0
inforsci at gmail dot com
4 years ago
convert 32bit HEX values into IEEE 754 floating point
<?php

$strHex
= "C45F82ED";

$bin = str_pad(base_convert($strHex, 16, 2), 32, "0", STR_PAD_LEFT);
$sign = $bin[0];
$exp = bindec(substr($bin, 1, 8)) - 127;
$man = (2 << 22) + bindec(substr($bin, 9, 23));

$dec = $man * pow(2, $exp - 23) * ($sign ? -1 : 1);

echo
"Answer = " . $dec . "<BR>\n";

?>
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0
Bob
5 years ago
Here is a function to convert an exponential-format float to a decimal-format float; e.g. 1.6e+12 to 1600000000000.
It will help addressing the problem specified by kjohnson above.
I have tested it, but not in any real world situation so any feedback/improvements/bug-reports would be appreciated.
<?php
function exp_to_dec($float_str)
// formats a floating point number string in decimal notation, supports signed floats, also supports non-standard formatting e.g. 0.2e+2 for 20
// e.g. '1.6E+6' to '1600000', '-4.566e-12' to '-0.000000000004566', '+34e+10' to '340000000000'
// Author: Bob
{
   
// make sure its a standard php float string (i.e. change 0.2e+2 to 20)
    // php will automatically format floats decimally if they are within a certain range
   
$float_str = (string)((float)($float_str));

   
// if there is an E in the float string
   
if(($pos = strpos(strtolower($float_str), 'e')) !== false)
    {
       
// get either side of the E, e.g. 1.6E+6 => exp E+6, num 1.6
       
$exp = substr($float_str, $pos+1);
       
$num = substr($float_str, 0, $pos);
       
       
// strip off num sign, if there is one, and leave it off if its + (not required)
       
if((($num_sign = $num[0]) === '+') || ($num_sign === '-')) $num = substr($num, 1);
        else
$num_sign = '';
        if(
$num_sign === '+') $num_sign = '';
       
       
// strip off exponential sign ('+' or '-' as in 'E+6') if there is one, otherwise throw error, e.g. E+6 => '+'
       
if((($exp_sign = $exp[0]) === '+') || ($exp_sign === '-')) $exp = substr($exp, 1);
        else
trigger_error("Could not convert exponential notation to decimal notation: invalid float string '$float_str'", E_USER_ERROR);
       
       
// get the number of decimal places to the right of the decimal point (or 0 if there is no dec point), e.g., 1.6 => 1
       
$right_dec_places = (($dec_pos = strpos($num, '.')) === false) ? 0 : strlen(substr($num, $dec_pos+1));
       
// get the number of decimal places to the left of the decimal point (or the length of the entire num if there is no dec point), e.g. 1.6 => 1
       
$left_dec_places = ($dec_pos === false) ? strlen($num) : strlen(substr($num, 0, $dec_pos));
       
       
// work out number of zeros from exp, exp sign and dec places, e.g. exp 6, exp sign +, dec places 1 => num zeros 5
       
if($exp_sign === '+') $num_zeros = $exp - $right_dec_places;
        else
$num_zeros = $exp - $left_dec_places;
       
       
// build a string with $num_zeros zeros, e.g. '0' 5 times => '00000'
       
$zeros = str_pad('', $num_zeros, '0');
       
       
// strip decimal from num, e.g. 1.6 => 16
       
if($dec_pos !== false) $num = str_replace('.', '', $num);
       
       
// if positive exponent, return like 1600000
       
if($exp_sign === '+') return $num_sign.$num.$zeros;
       
// if negative exponent, return like 0.0000016
       
else return $num_sign.'0.'.$zeros.$num;
    }
   
// otherwise, assume already in decimal notation and return
   
else return $float_str;
}
?>
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-2
rob at willo dot org
5 years ago
PHP will parse ".123" with no leading digit; just a decimal point. For a command-line example:

php -r "echo 1 + .123;"

The regular expression provided above does not parse it.
My correction is:

EXPONENT_DNUM = "[+-]?({DNUM} | ({LNUM} | {DNUM}) [eE][+-]? {LNUM})"

NOTE: {LNUM} by itself is an integer, not a floating point.
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-2
pcunha at gmail dot com
1 year ago
To simply convert 32 bits float from hex to float:

<?php
function hexfloat ($hex){
    return (
unpack("f", pack('H*',$hex))[1]);
}
?>

This may be useful for arduino interface with php.
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-3
pgarvin76+phpmanual at gmail dot com
4 years ago
When converting from float to string trailing zeros will be dropped. Consider the following example. Tested on PHP 5.3.1.

<?php
$a
= 5.00500;
$b = 30.00;
echo
"a = $a\n";
echo
"b = $b\n";
/* outputs:
a = 5.005
b = 30
*/
?>
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-2
info at forrest79 dot net
5 years ago
My BIN to FLOAT (IEEE754), the first one doesn't work for me:

<?php
       
function binToFloat($bin) {
            if(
strlen($bin) > 32) {
                return
false;
            } else if(
strlen($bin) < 32) {
               
$bin = str_repeat('0', (32 - strlen($bin))) . $bin;
            }

           
$sign = 1;
            if(
intval($bin[0]) == 1) {
               
$sign = -1;
            }

           
$binExponent = substr($bin, 1, 8);
           
$exponent = -127;
            for(
$i = 0; $i < 8; $i++) {
               
$exponent += (intval($binExponent[7 - $i]) * pow(2, $i));
            }

           
$binBase = substr($bin, 9);           
           
$base = 1.0;
            for(
$x = 0; $x < 23; $x++) {
               
$base += (intval($binBase[$x]) * pow(0.5, ($x + 1)));
            }

           
$float = (float) $sign * pow(2, $exponent) * $base;

            return
$float;
        }
?>
up
-3
manasseh at smartcomputerinc.com
3 years ago
I found that 00000000 hex was converting to 1.0 decimal. From the Wikipedia article on IEEE-754 floating point:

The true significand includes 23 fraction bits to the right of the binary point and an implicit leading bit (to the left of the binary point) with value 1 unless the exponent is stored with all zeros.

In hex2float32n, replace:

      $intnumber=bindec("1".$binint);

with

   if ($exp <> -127)
      { $intnumber=bindec("1".$binint); };

and then 00000000 works correctly without affecting "normal" numbers.
up
-4
TRI0N
8 years ago
Here is a simple formula to break down a number and get rid of the decimal values.  I built this to take a number in seconds and convert it to a readable value for Server Uptimes.

<?php
$day
= floor(($uptime / 86400)*1.0) ;
$calc1 = $day * 86400 ;
$calc2 = $uptime - $calc1 ;
$hour = floor(($calc2 / 3600)*1.0) ;
if (
$hour < 10) {
$hour = "0".$hour ;
}
$calc3 = $hour * 3600 ;
$calc4 = $calc2 - $calc3 ;
$min = floor(($calc4 / 60)*1.0) ;
if (
$min < 10) {
$min = "0".$min ;
}
$calc5 = $min * 60 ;
$sec = floor(($calc4 - $calc5)*1.0) ;
if (
$min < 10) {
$sec = "0".$sec ;
}
$uptime2 = $day." Days, ".$hour.":".$min.":".$sec ;
?>

Place this where you want the results to be seen:
<?php echo $uptime2 ; ?>

For a Value of 1455587 seconds the results will show as followed:
16 Days, 20:19:47

Enjoy
up
-5
francois dot barbier at gmail dot com
5 years ago
As "m dot lebkowski+php at gmail dot com" (http://www.php.net/language.types.float#81416) noted 9 comments below :

When PHP converts a float to a string, the decimal separator used depends on the current locale conventions.

However, to declare a floating point number, one must always use a full stop otherwhise the code would be locale dependent (imagine the nightmare):
<?php
$float
= 1.5;           // float(1.5)
$float = 1,5;           // Parse error: syntax error, unexpected ','
$float = (float) '1.5'; // float(1.5)
$float = (float) '1,5'; // float(1)
?>

Now, if you have a string containing a localized number, you can convert it back to a floating point number using the following function:
<?php
/**
* Convert a localized number string into a floating point number
*
* @param      string $sNumber The localized number string to convert.
* @return     float The converted number.
*/
function str2num($sNumber)
{
   
$aConventions = localeConv();
   
$sNumber = trim((string) $sNumber);
   
$bIsNegative = (0 === $aConventions['n_sign_posn'] && '(' === $sNumber{0} && ')' === $sNumber{strlen($sNumber) - 1});
   
$sCharacters = $aConventions['decimal_point'].
                  
$aConventions['mon_decimal_point'].
                  
$aConventions['negative_sign'];
   
$sNumber = preg_replace('/[^'.preg_quote($sCharacters).'\d]+/', '', trim((string) $sNumber));
   
$iLength = strlen($sNumber);
    if (
strlen($aConventions['decimal_point']))
    {
       
$sNumber = str_replace($aConventions['decimal_point'], '.', $sNumber);
    }
    if (
strlen($aConventions['mon_decimal_point']))
    {
       
$sNumber = str_replace($aConventions['mon_decimal_point'], '.', $sNumber);
    }
   
$sNegativeSign = $aConventions['negative_sign'];
    if (
strlen($sNegativeSign) && 0 !== $aConventions['n_sign_posn'])
    {
       
$bIsNegative = ($sNegativeSign === $sNumber{0} || $sNegativeSign === $sNumber{$iLength - 1});
        if (
$bIsNegative)
        {
           
$sNumber = str_replace($aConventions['negative_sign'], '', $sNumber);
        }
    }
   
$fNumber = (float) $sNumber;
    if (
$bIsNegative)
    {
       
$fNumber = -$fNumber;
    }
    return
$fNumber;
}
?>

Example:
<?php
setLocale
(LC_ALL, 'fr_BE.UTF-8'); // decimal separator is now a comma
$float = -123456.789;
$string = (string) $float;
var_dump($float);           // float(-123456,789)
var_dump($string);          // string(11) "-123456,789"
var_dump((float) $string);  // float(-123456)
var_dump(str2num($string)); // float(-123456,789)
?>

It also works with strings returned by the number_format() function:
<?php
setLocale
(LC_ALL, 'fr_BE.UTF-8'); // decimal separator is now a comma
$conv = localeconv();
$float = -123456.789;
$string = $conv['int_curr_symbol'].number_format($float, $conv['frac_digits'], $conv['decimal_point'], $conv['thousands_sep']);
var_dump($float);           // float(-123456,789)
var_dump($string);          // string(15) "EUR -123.456,79"
var_dump((float) $string);  // float(0)
var_dump(str2num($string)); // float(-123456,79)
?>
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-6
reinaldorock at yahoo dot com dot br
2 years ago
Convert locale string into float number

<?php
function str2num($str){
  if(
strpos($str, '.') < strpos($str,',')){
           
$str = str_replace('.','',$str);
           
$str = strtr($str,',','.');           
        }
        else{
           
$str = str_replace(',','',$str);           
        }
        return (float)
$str;
}

str2num('25,01'); //25.01
str2num('2.5,01'); //25.01
str2num('25.01'); //25.01
str2num('2,5.01'); //25.01
?>
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