After a couple of minutes i've realize the bug that i was having: the magic 2147483647 number, that upper limit for integer type on PHP/32. I need to manage biggers number in my function:
public function albumExists($name) // e.g. 104112826372452
{
$albums = $this->getAlbums();
// If $name is int, search the key in $albums
if(is_int($name) && ($found = array_key_exists($id = intval($name), $albums)))
return ($found ? $id : false);
// Start looking for $name as string
foreach($album as $id => $a) if ($a->name == $name) return intval($id);
return false; // Found nothing
}
in order to give the ability to search both by id and name. But intval() will always return the upper limit. How can handle quite big numbers like, say, 104112826372452? Ideas?
EDIT: usage example:
$album = $fb->createAlbum('Test Album'); // Will return album id
// The use albumExists to check if id exists
$photo1 = $fb->uploadPhoto('mypic1.png', null, $album);
$photo2 = $fb->uploadPhoto('mypic2.png', null, 'Test Album'); // find or create
If you're converting to an int for sanity purposes (so it appears), perhaps you could just adjust it to evaluate it purely on it's numeric basis instead of int datatype:
if(ctype_digit($name) && ($found = array_key_exists($id = $name, $albums)))
return ($found ? $id : false);
//etc
Actually, should this work too?
if(ctype_digit($name) && ($found = array_key_exists($name, $albums)))
return ($found ? $name: false);
//etc
As workaround you can use the gmp or bcmath functions for that.
It's not quite clear why you insist on casting to PHP integers. Just leave your database numbering as strings, when don't need to calculate with them. Not everything that looks like a number needs to be represented as number.
I guess your real problem is the differentation with is_int(). Just use is_numeric() in its place, which works with arbitrary-length numeric strings and does not depend on integer-casted values.
An int has an upper limit, and bigger numbers will be represented as floats, which are imprecise and therefore a bad idea to use in this situation. Use a string to store such numbers and the BC Math extension if you need to do calculations on it.
Unfornuately PHP int type can only go upto 2147483647 but PHP float can hold integers upto 10000000000000
Check out php.net
http://php.net/manual/en/language.types.integer.php
UPDATE
PHP.net says that a float can accurately hold an integer upto 10000000000000. Im not sure if float has an upper limit though.
One option is to run PHP on a 64bit OS as the in size is determined by the underlying operating system. This is obviously dependent if you can get access to 64bit hardware, one thing to note is that this will be faster than using gmp/bcmath but unless pure speed is your aim it probably won't be an issue for you
Related
I know you can tell a variable to go to a certain number of decimal places using:
string number_format ( float $number [, int $decimals = 3 ] )
However, I cannot find a way of doing this en masse for all numbers. Since I have hundreds of variables, all of which need to have the same number of decimal places (whether it means rounding or extending zeros), I would like to be able to just tell it to automatically perform this command across the board instead of typing in the above command for all variables.
Does this function exist, or am I forced to type it all out the long way? Is there maybe a line in the .ini file that I could change if there is no command?
Thanks in advance.
I'm not storing these numbers in a database - I'm echo-ing them on the screen and sending an email.
(There is an equation going on from user input being generated by an HTML form).
The person receiving the email has asked that all numbers be rounded to the third decimal, whether that means rounding off at the thousandths or extending zeros to the thousandths if it only needed whole numbers, tenths, or hundredths. There are literally hundreds of individual variables, i.e. $number1, $number2, etc.
If you are talking about all numbers applied to string variables in your script you could run this line:
if(is_int($value) || is_float($value)){
$value = number_format ( float $number ,3 );
}
Obviously as you reference strings you can also run a similar query to check if your string is a floating numeric:
$values = get_defined_vars();
foreach ($values as $key=>$value){
if(is_string($value) && (float)$value == (string)$value){
$value = number_format ((float)$value , 3 );
}
/***
Save over the original script variables with the edited ones.
Note double dollar
***/
$$key = $value;
}
unset($values,$value,$key);
You could do with reading that in base-2 (computer storage) floating point numbers are inherently stored inaccurately, read http://floating-point-gui.de/ .
Also, really, why would you need this seemingly needless precision?
But then at what stage do you run this command, at the start of your script when the values are mostly empty? Or at the end when the values are mostly been used and no longer active?
I think my answer answers your question but I think that your question does not actually articulate your issue.
In response to the comment / edited qestion:
Simply rather than using $values = get_defined_vars(); use the values from saving the inputs into an array and doing foreach above through the array.
$values = array(array of numbers);
foreach ($values as &$value){
if(is_string($value) && (float)$value == (string)$value){
$value = number_format ((float)$value , 3 );
}
}
unset($value,$key);
This will update all values in the array to being of the spcified numerical placements.
You can use the decimal extension to achieve this, with a central place to create and format. Something like this:
class Number
{
public static function create($value, $precision = Decimal::DEFAULT_PRECISION): Decimal
{
return new Decimal($value, $precision);
}
public static function format(Decimal $decimal, int $places = 3): string
{
return $decimal->toFixed(3);
}
}
I'm doing a calculation in PHP using bcmath, and need to raise e by a fractional exponent. Unfortunately, bcpow() only accepts integer exponents. The exponent is typically higher precision than a float will allow, so normal arithmetic functions won't cut it.
For example:
$e = exp(1);
$pow = "0.000000000000000000108420217248550443400745280086994171142578125";
$result = bcpow($e, $pow);
Result is "1" with the error, "bc math warning: non-zero scale in exponent".
Is there another function I can use instead of bcpow()?
Your best bet is probably to use the Taylor series expansion. As you noted, PHP's bcpow is limited to raising to integer exponentiation.
So what you can do is roll your own bc factorial function and use the wiki page to implement a Taylor series expansion of the exponential function.
function bcfac($num) {
if ($num==0) return 1;
$result = '1';
for ( ; $num > 0; $num--)
$result = bcmul($result,$num);
return $result;
}
$mysum = '0';
for ($i=0; $i<300; $i++) {
$mysum = bcadd($mysum, bcdiv(bcpow($pow,$i), bcfac($i)) );
}
print $mysum;
Obviously, the $i<300 is an approximation for infinity... You can change it to suit your performance needs.
With $i=20, I got
1.00000000000000000010842021724855044340662275184110560868263421994092888869270293594926619547803962155136242752708629105688492780863293090291376157887898519458498571566021915144483905034693109606778068801680332504212458366799913406541920812216634834265692913062346724688397654924947370526356787052264726969653983148004800229537555582281617497990286595977830803702329470381960270717424849203303593850108090101578510305396615293917807977774686848422213799049363135722460179809890014584148659937665374616
This is comforting since that small of an exponent should yield something really close to 1.0.
Old question, but people might still be interested nonetheless.
So Kevin got the right idea with the Taylor-polynomial, but when you derive your algorithm from it directly, you can get into trouble, mainly your code gets slow for long input-strings when using large cut-off values for $i.
Here is why:
At every step, by which I mean with each new $i, the code calls bcfac($i). Everytime bcfac is called it performs $i-1 calculations. And $i goes all the way up to 299... that's almost 45000 operations! Not your quick'n'easy floating point operations, but slow BC-string-operations - if you set bcscale(100) your bcmul has to handle up to 10000 pairs of chars!
Also bcpow slows down with increasing $i, too. Not as much as bcfac, because it propably uses something akin to the square-and-multiply method, but it still adds something.
Overall the time required grows quadraticly with the number of polynomial terms computed.
So... what to do?
Here's a tip:
Whenever you handle polynomials, especially Taylor-polynomials, use the Horner method.
It converts this: exp(x) = x^0/0! + x^1/1! + x^2/2! + x^3/3! + ...
...into that: exp(x) = ((( ... )*x/3+1 )*x/2+1 )*x/1+1
And suddenly you don't need any powers or factorials at all!
function bc_exp($number) {
$result = 1;
for ($i=299; $i>0; $i--)
$result = bcadd(bcmul(bcdiv($result, $i), $number), 1);
return $result;
}
This needs only 3 bc-operations for each step, no matter what $i is.
With a starting value of $i=299 (to calculate exp with the same precision as kevin's code does) we now only need 897 bc-operations, compared to more than 45000.
Even using 30 as cut-off instead of 300, we now only need 87 bc-operations while the other code still needs 822 for the factorials alone.
Horner's Method saving the day again!
Some other thoughts:
1) Kevin's code would propably crash with input="0", depending on how bcmath handles errors, because the code trys bcpow(0,0) at the first step ($i=0).
2) Larger exponents require longer polynomials and therefore more iterations, e.g. bc_exp(300) will give a wrong answer, even with $i=299, whyle something like bc_exp(3) will work fine and dandy.
Each term adds x^n/n! to the result, so this term has to get small before the polynomial can start to converge. Now compare two consecutive terms:
( x^(n+1)/(n+1)! ) / ( x^n/n! ) = x/n
Each summand is larger than the one before by a factor of x/n (which we used via the Horner method), so in order for x^(n+1)/(n+1)! to get small x/n has to get small as well, which is only the case when n>x.
Inconclusio: As long as the number of iterations is smaller than the input value, the result will diverge. Only when you add steps until your number of iterations gets larger than the input, the algorithm starts to slowly converge.
In order to reach results that can satisfie someone who is willing to use bcmath, your $i needs to be significantly larger then your $number. And that's a huge proplem when you try to calculate stuff like e^346674567801
A solution is to divide the input into its integer part and its fraction part.
Than use bcpow on the integer part and bc_exp on the fraction part, which now converges from the get-go since the fraction part is smaller than 1. In the end multiply the results.
e^x = e^(intpart+fracpart) = e^intpart * e^fracpart = bcpow(e,intpart) * bc_exp(fracpart)
You could even implement it directly into the code above:
function bc_exp2($number) {
$parts = explode (".", $number);
$fracpart = "0.".$parts[1];
$result = 1;
for ($i=299; $i>0; $i--)
$result = bcadd(bcmul(bcdiv($result, $i), $fracpart), 1);
$result = bcmul(bcpow(exp(1), $parts[0]), $result);
return $result;
}
Note that exp(1) gives you a floating-point number which propably won't satisfy your needs as a bcmath user. You might want to use a value for e that is more accurate, in accordance with your bcscale setting.
3) Talking about numbers of iterations: 300 will be overkill in most situations while in some others it might not even be enough. An algorithm that takes your bcscale and $number and calculates the number of required iterations would be nice. Alraedy got some ideas involving log(n!), but nothing concrete yet.
4) To use this method with an arbitrary base you can use a^x = e^(x*ln(a)).
You might want to divide x into its intpart and fracpart before using bc_exp (instead of doing that within bc_exp2) to avoid unneccessary function calls.
function bc_pow2($base,$exponent) {
$parts = explode (".", $exponent);
if ($parts[1] == 0){
$result = bcpow($base,$parts[0]);
else $result = bcmul(bc_exp(bcmul(bc_ln($base), "0.".$parts[1]), bcpow($base,$parts[0]);
return result;
}
Now we only need to program bc_ln. We can use the same strategy as above:
Take the Taylor-polynomial of the natural logarithm function. (since ln(0) isn't defined, take 1 as developement point instead)
Use Horner's method to drasticly improve performance.
Turn the result into a loop of bc-operations.
Also make use of ln(x) = -ln(1/x) when handling x > 1, to guarantee convergence.
usefull functions(don't forget to set bcscale() before using them)
function bc_fact($f){return $f==1?1:bcmul($f,bc_fact(bcsub($f, '1')));}
function bc_exp($x,$L=50){$r=bcadd('1.0',$x);for($i=0;$i<$L;$i++){$r=bcadd($r,bcdiv(bcpow($x,$i+2),bc_fact($i+2)));}return $r;}#e^x
function bc_ln($x,$L=50){$r=0;for($i=0;$i<$L;$i++){$p=1+$i*2;$r = bcadd(bcmul(bcdiv("1.0",$p),bcpow(bcdiv(bcsub($x,"1.0"),bcadd($x,"1.0")),$p)),$r);}return bcmul("2.0", $r);}#2*Sum((1/(2i+1))*(((x-1)/x+1)^(2i+1)))
function bc_pow($x,$p){return bc_exp(bcmul((bc_ln(($x))), $p));}
How can the below be possible:
$varnum = 4;
if( $varnum/4 - floor($varnum/4) !== 0){
echo 'foo';
}
This echoes 'foo' on my server running PHP 5.1.6. If i change the operator to == I get the same results.
I have no idea why, but could it possibly be because "==" is "equals" and "!==" is "Not identical"? How then would I make them identical? I guess in javaScript I would "parseInt", but there is no such thing in PHP, right?
The reason this fails is because in PHP, the floor function returns a float, despite the fact that the value is always a whole number. You can see this in the documentation here: http://php.net/manual/en/function.floor.php
You're doing a fixed type comparison of that float to an integer zero, so the result is false, regardless of whether the value is actually zero.
To fix this, either:
cast the output of floor to an integer - either intval(float(...)) or (int)float(..)
use != instead of !==.
use 0.0 instead of just 0 to compare against.
In case you're wondering why floor() would return a float rather than an integer, it's because the input is a float. The float data type has a larger possible range than integer, and thus it is possible to call floor() on a value that would be too big to hold in an integer. Therefore it would not be safe for the function to return an integer; it returns a float instead so that it can guarantee the result will be correct.
It may seem odd at first glance, but hopefully that explains the logic behind it for you.
What is it you are trying to accomplish? If you are trying to see if $varnum is divisible by four then use modulus, so...
$varnum = 4;
if ($varnum % 4 != 0) {
echo "foo - $varnum is divisible by 4";
}
You original post should use '!=' versus '!==', like this:
$varnum = 4;
if( $varnum/4 - floor($varnum/4) != 0){
echo 'foo';
}
rand(1,N) but excluding array(a,b,c,..),
is there already a built-in function that I don't know or do I have to implement it myself(how?) ?
UPDATE
The qualified solution should have gold performance whether the size of the excluded array is big or not.
No built-in function, but you could do this:
function randWithout($from, $to, array $exceptions) {
sort($exceptions); // lets us use break; in the foreach reliably
$number = rand($from, $to - count($exceptions)); // or mt_rand()
foreach ($exceptions as $exception) {
if ($number >= $exception) {
$number++; // make up for the gap
} else /*if ($number < $exception)*/ {
break;
}
}
return $number;
}
That's off the top of my head, so it could use polishing - but at least you can't end up in an infinite-loop scenario, even hypothetically.
Note: The function breaks if $exceptions exhausts your range - e.g. calling randWithout(1, 2, array(1,2)) or randWithout(1, 2, array(0,1,2,3)) will not yield anything sensible (obviously), but in that case, the returned number will be outside the $from-$to range, so it's easy to catch.
If $exceptions is guaranteed to be sorted already, sort($exceptions); can be removed.
Eye-candy: Somewhat minimalistic visualisation of the algorithm.
I don't think there's such a function built-in ; you'll probably have to code it yourself.
To code this, you have two solutions :
Use a loop, to call rand() or mt_rand() until it returns a correct value
which means calling rand() several times, in the worst case
but this should work OK if N is big, and you don't have many forbidden values.
Build an array that contains only legal values
And use array_rand to pick one value from it
which will work fine if N is small
Depending on exactly what you need, and why, this approach might be an interesting alternative.
$numbers = array_diff(range(1, N), array(a, b, c));
// Either (not a real answer, but could be useful, depending on your circumstances)
shuffle($numbers); // $numbers is now a randomly-sorted array containing all the numbers that interest you
// Or:
$x = $numbers[array_rand($numbers)]; // $x is now a random number selected from the set of numbers you're interested in
So, if you don't need to generate the set of potential numbers each time, but are generating the set once and then picking a bunch of random number from the same set, this could be a good way to go.
The simplest way...
<?php
function rand_except($min, $max, $excepting = array()) {
$num = mt_rand($min, $max);
return in_array($num, $excepting) ? rand_except($min, $max, $excepting) : $num;
}
?>
What you need to do is calculate an array of skipped locations so you can pick a random position in a continuous array of length M = N - #of exceptions and easily map it back to the original array with holes. This will require time and space equal to the skipped array. I don't know php from a hole in the ground so forgive the textual semi-psudo code example.
Make a new array Offset[] the same length as the Exceptions array.
in Offset[i] store the first index in the imagined non-holey array that would have skipped i elements in the original array.
Now to pick a random element. Select a random number, r, in 0..M the number of remaining elements.
Find i such that Offset[i] <= r < Offest[i+i] this is easy with a binary search
Return r + i
Now, that is just a sketch you will need to deal with the ends of the arrays and if things are indexed form 0 or 1 and all that jazz. If you are clever you can actually compute the Offset array on the fly from the original, it is a bit less clear that way though.
Maybe its too late for answer, but I found this piece of code somewhere in my mind when trying to get random data from Database based on random ID excluding some number.
$excludedData = array(); // This is your excluded number
$maxVal = $this->db->count_all_results("game_pertanyaan"); // Get the maximum number based on my database
$randomNum = rand(1, $maxVal); // Make first initiation, I think you can put this directly in the while > in_array paramater, seems working as well, it's up to you
while (in_array($randomNum, $excludedData)) {
$randomNum = rand(1, $maxVal);
}
$randomNum; //Your random number excluding some number you choose
This is the fastest & best performance way to do it :
$all = range($Min,$Max);
$diff = array_diff($all,$Exclude);
shuffle($diff );
$data = array_slice($diff,0,$quantity);
I am not familiar with PHP at all and had a quick question.
I have 2 variables pricePerUnit and InvoicedUnits. Here's the code that is setting these to values:
$InvoicedUnits = ((string) $InvoiceLineItem->InvoicedUnits);
$pricePerUnit = ((string) $InvoiceLineItem->PricePerUnit);
If I output this, I get the correct values. Lets say 5000 invoiced units and 1.00 for price.
Now, I need to show the total amount spent. When I multiply these two together it doesn't work (as expected, these are strings).
But I have no clue how to parse/cast/convert variables in PHP.
What should I do?
$rootbeer = (float) $InvoicedUnits;
Should do it for you. Check out Type-Juggling. You should also read String conversion to Numbers.
You want the non-locale-aware floatval function:
float floatval ( mixed $var ) - Gets the float value of a string.
Example:
$string = '122.34343The';
$float = floatval($string);
echo $float; // 122.34343
Well, if user write 1,00,000 then floatvar will show error. So -
floatval(preg_replace("/[^-0-9\.]/","",$input));
This is much more reliable.
Usage :
$input = '1,03,24,23,434,500.6798633 this';
echo floatval(preg_replace("/[^-0-9\.]/","",$input));
Dealing with markup in floats is a non trivial task. In the English/American notation you format one thousand plus 46*10-2:
1,000.46
But in Germany you would change comma and point:
1.000,46
This makes it really hard guessing the right number in multi-language applications.
I strongly suggest using Zend_Measure of the Zend Framework for this task. This component will parse the string to a float by the users language.
you can follow this link to know more about How to convert a string/number into number/float/decimal in PHP.
HERE IS WHAT THIS LINK SAYS...
Method 1: Using number_format() Function. The number_format() function is used to convert a string into a number. It returns the formatted number on success otherwise it gives E_WARNING on failure.
$num = "1000.314";
//Convert string in number using
//number_format(), function
echo number_format($num), "\n";
//Convert string in number using
//number_format(), function
echo number_format($num, 2);
Method 2: Using type casting: Typecasting can directly convert a string into a float, double, or integer primitive type. This is the best way to convert a string into a number without any function.
// Number in string format
$num = "1000.314";
// Type cast using int
echo (int)$num, "\n";
// Type cast using float
echo (float)$num, "\n";
// Type cast using double
echo (double)$num;
Method 3: Using intval() and floatval() Function. The intval() and floatval() functions can also be used to convert the string into its corresponding integer and float values respectively.
// Number in string format
$num = "1000.314";
// intval() function to convert
// string into integer
echo intval($num), "\n";
// floatval() function to convert
// string to float
echo floatval($num);
Method 4: By adding 0 or by performing mathematical operations. The string number can also be converted into an integer or float by adding 0 with the string. In PHP, performing mathematical operations, the string is converted to an integer or float implicitly.
// Number into string format
$num = "1000.314";
// Performing mathematical operation
// to implicitly type conversion
echo $num + 0, "\n";
// Performing mathematical operation
// to implicitly type conversion
echo $num + 0.0, "\n";
// Performing mathematical operation
// to implicitly type conversion
echo $num + 0.1;
Use this function to cast a float value from any kind of text style:
function parseFloat($value) {
return floatval(preg_replace('#^([-]*[0-9\.,\' ]+?)((\.|,){1}([0-9-]{1,3}))*$#e', "str_replace(array('.', ',', \"'\", ' '), '', '\\1') . '.\\4'", $value));
}
This solution is not dependant on any locale settings. Thus for user input users can type float values in any way they like. This is really helpful e.g. when you have a project wich is in english only but people all over the world are using it and might not have in mind that the project wants a dot instead of a comma for float values.
You could throw javascript in the mix and fetch the browsers default settings but still many people set these values to english but still typing 1,25 instead of 1.25 (especially but not limited to the translation industry, research and IT)
I was running in to a problem with the standard way to do this:
$string = "one";
$float = (float)$string;
echo $float; : ( Prints 0 )
If there isn't a valid number, the parser shouldn't return a number, it should throw an error. (This is a condition I'm trying to catch in my code, YMMV)
To fix this I have done the following:
$string = "one";
$float = is_numeric($string) ? (float)$string : null;
echo $float; : ( Prints nothing )
Then before further processing the conversion, I can check and return an error if there wasn't a valid parse of the string.
For the sake of completeness, although this question is ancient, it's worth mentioning the filter_var() set of functions, which should not only handle the formatting bits itself, but also validate or sanitise the output, thus being safer to use in the context of a form being filled in by users (or, eventually, a database that might have some corrupted/inconsistent fields):
$InvoicedUnits = (float) filter_var($InvoiceLineItem->InvoicedUnits,
FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION));
$pricePerUnit = (float) filter_var($InvoiceLineItem->PricePerUnit,
FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION));
printf("The total is: %.2f\n", $InvoicedUnits * $pricePerUnit); // both are now floats and the result is a float, formatted to two digits after the decimal sign.
This sanitises the output (which will still remain a string) and will accept the current locale's setting of the decimal separator (e.g. dot vs. comma); also, there are more options on the PHP manual for validation (which will automatically convert the result to a float if valid). The results will be slightly different for different scenarios — e.g. if you know in advance that the $InvoiceLineItem will only have valid digits and symbols for floating-point numbers, or if you need to 'clean up' the field first, getting rid of whitespace, stray characters (such as currency symbols!), and so forth.
Finally, if you wish to have nicely-formatted output — since the total is expressed in a currency — you should also take a look at the built-in NumberFormatter class, and do something like:
$InvoicedUnits = (float) filter_var($InvoiceLineItem->InvoicedUnits,
FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION));
$pricePerUnit = (float) filter_var($InvoiceLineItem->PricePerUnit,
FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION));
$fmt = new NumberFormatter('de_DE', NumberFormatter::CURRENCY);
echo 'Total is: ' . $fmt->formatCurrency($InvoicedUnits * $pricePerUnit, 'EUR') . PHP_EOL;
This will also handle thousand separators (spaces, dots, commas...) according to the configured locale, and other similar fancy things.
Also, if you wish, you can use '' (the empty string) for the default locale string (set either by the server or optionally by the browser) and $fmt->getSymbol(NumberFormatter::INTL_CURRENCY_SYMBOL) to get the default 3-letter currency code (which might not be what you want, since usually prices are given in a specific currency — these functions do not take currency exchange rates into account!).
If you need to handle values that cannot be converted separately, you can use this method:
try {
// use + 0 if you are accounting in cents
$doubleValue = trim($stringThatMightBeNumeric) + 0.0;
} catch (\Throwable $th) {
// bail here if you need to
}