# Math İşlevleri

## İçindekiler

• abs — Absolute value
• acos — Arc cosine
• acosh — Inverse hyperbolic cosine
• asin — Arc sine
• asinh — Inverse hyperbolic sine
• atan2 — Arc tangent of two variables
• atan — Arc tangent
• atanh — Inverse hyperbolic tangent
• base_convert — Convert a number between arbitrary bases
• bindec — Binary to decimal
• ceil — Round fractions up
• cos — Cosine
• cosh — Hyperbolic cosine
• decbin — Decimal to binary
• dechex — Decimal to hexadecimal
• decoct — Decimal to octal
• deg2rad — Converts the number in degrees to the radian equivalent
• exp — Calculates the exponent of e
• expm1 — Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zero
• floor — Round fractions down
• fmod — Returns the floating point remainder (modulo) of the division of the arguments
• getrandmax — Show largest possible random value
• hexdec — Hexadecimal to decimal
• hypot — Calculate the length of the hypotenuse of a right-angle triangle
• intdiv — Integer division
• is_finite — Finds whether a value is a legal finite number
• is_infinite — Finds whether a value is infinite
• is_nan — Finds whether a value is not a number
• lcg_value — Combined linear congruential generator
• log10 — Base-10 logarithm
• log1p — Returns log(1 + number), computed in a way that is accurate even when the value of number is close to zero
• log — Natural logarithm
• max — Find highest value
• min — Find lowest value
• mt_getrandmax — Show largest possible random value
• mt_rand — Generate a random value via the Mersenne Twister Random Number Generator
• mt_srand — Seeds the Mersenne Twister Random Number Generator
• octdec — Octal to decimal
• pi — Get value of pi
• pow — Exponential expression
• rad2deg — Converts the radian number to the equivalent number in degrees
• rand — Generate a random integer
• round — Rounds a float
• sin — Sine
• sinh — Hyperbolic sine
• sqrt — Square root
• srand — Seed the random number generator
• tan — Tangent
• tanh — Hyperbolic tangent

### User Contributed Notes 52 notes

nazgul26 (at_sign) windfox dot net
15 years ago
This code will convert a decimal to it's fraction equivalent. The precision can be set by changing PRECISION.

<?php
define
(PRECISION, .01);

\$count=0;
\$result=array();
decimalToFraction(\$_REQUEST['dec'],\$count,&\$result);
\$count = count(\$result);
\$simp_fract = simplifyFraction(\$result,\$count,1,\$result[\$count]);

echo
\$simpl_fract;

// Start of functions

/*
Converts a decimal to unsimplified fraction represented in an array
*/
function decimalToFraction(\$decimal,\$count,\$result) {

\$a = (1/\$decimal);

\$b = ( \$a - floor(\$a)  );

\$count++;
if (
\$b > .01 && \$count <= 5) decimalToFraction(\$b,\$count,&\$result);

\$result[\$count] = floor(\$a);
}

/*
Simplifies a fraction in an array form that is returned from
decimalToFraction
*/
function simplifyFraction(\$fraction,\$count,\$top,\$bottom) {

\$next = \$fraction[\$count-1];

\$a = (\$bottom * \$next) + \$top;

\$top = \$bottom;

\$bottom = \$a;

\$count--;
if (
\$count > 0) simplifyFraction(\$fraction,\$count,\$top,\$bottom);
else {
return
"<font size=1>\$bottom/\$top</font>";
}
}
?>
jbeardsl [found_at] gte [d0t] net
15 years ago
I was looking for a truncate function. Not finding one, I wrote my own. Since it deals with everything as a number, I imagine it's faster than the alternative of using string functions. HTH...

<?php
function truncate (\$num, \$digits = 0) {

//provide the real number, and the number of
//digits right of the decimal you want to keep.

\$shift = pow(10, \$digits);
return ((
floor(\$num * \$shift)) / \$shift);
}
?>
peter-stangl at t-online dot de
12 years ago
I needed to approximate an integral because i was not able to calculate it, so i wrote this function. It approximates an integral with the composite Simpson's rule.

<?php

function simpsonf(\$x){
// returns f(x) for integral approximation with composite Simpson's rule

return(pow((1+pow(\$x, (-4))), 0.5));
}
function
simpsonsrule(\$a, \$b, \$n){
// approximates integral_a_b f(x) dx with composite Simpson's rule with \$n intervals
// \$n has to be an even number
// f(x) is defined in "function simpsonf(\$x)"

if(\$n%2==0){

\$h=(\$b-\$a)/\$n;

\$S=simpsonf(\$a)+simpsonf(\$b);

\$i=1;
while(
\$i <= (\$n-1)){

\$xi=\$a+\$h*\$i;
if(
\$i%2==0){

\$S=\$S+2*simpsonf(\$xi);
}
else{

\$S=\$S+4*simpsonf(\$xi);
}

\$i++;
}
return(
\$h/3*\$S);
}
else{
return(
'\$n has to be an even number');
}
}

?>
pat.mat AT sympatico DOT com
14 years ago
For people interest in Differential Equations, I've done a function that receive a string like: x^2+x^3 and put it in
2x+3x^2 witch is the differantial of the previous equation.

In the code there is one thing missing: the \$string{\$i} is often going outOfBound (Uninitialized string offset: 6 in...)
if your error setting is set a little too high... I just dont know how to fix this.

So there is the code for differential equation with (+ and -) only:

<?
function differentiel(\$equa)
{
\$equa = strtolower(\$equa);
echo "Equation de depart: ".\$equa."<br>";
\$final = "";

for(\$i = 0; \$i < strlen(\$equa); \$i++)
{
//Make a new string from the receive \$equa
if(\$equa{\$i} == "x" && \$equa{\$i+1} == "^")
{
\$final .= \$equa{\$i+2};
\$final .= "x^";
\$final .= \$equa{\$i+2}-1;
}
elseif(\$equa{\$i} == "+" || \$equa{\$i} == "-")
{
\$final .= \$equa{\$i};
}
elseif(is_numeric(\$equa{\$i}) && \$i == 0)
{
//gerer parenthese et autre terme generaux + gerer ^apres: 2^2
\$final .= \$equa{\$i}."*";
}
elseif(is_numeric(\$equa{\$i}) && \$i > 0 && \$equa{\$i-1} != "^")
{
//gerer ^apres: 2^2
\$final .= \$equa{\$i}."*";
}
elseif(\$equa{\$i} == "^")
{
continue;
}
elseif(is_numeric(\$equa{\$i}) && \$equa{\$i-1} == "^")
{
continue;
}
else
{
if(\$equa{\$i} == "x")
{
\$final .= 1;
}
else
{
\$final .= \$equa{\$i};
}
}
}
//
//Manage multiplication add in the previous string \$final
//
\$finalMul = "";
for(\$i = 0; \$i < strlen(\$final); \$i++)
{
if(is_numeric(\$final{\$i}) && \$final{\$i+1} == "*" && is_numeric(\$final{\$i+2}))
{
\$finalMul .= \$final{\$i}*\$final{\$i+2};
}
elseif(\$final{\$i} == "*")
{
continue;
}
elseif(is_numeric(\$final{\$i}) && \$final{\$i+1} != "*" && \$final{\$i-1} == "*")
{
continue;
}
else
{
\$finalMul .= \$final{\$i};
}
}
echo "equa final: ".\$finalMul;
}
?>

I know this is not optimal but i've done this quick :)
If you guys have any comment just email me.
I also want to do this fonction In C to add to phpCore maybe soon...
Patoff
sabry97000 at gmail dot com
1 month ago
And the reason I needed a Factorial function is because I there were no nPr or nCr functions native to PHP, either.

function n_pick_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (fact(\$n)/fact(\$n-\$r));}
function n_choose_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (n_pick_r(\$n,\$r)/fact(\$r));}

Hope that helps someone!
exmple www.pqlme.com php
tmpa at yahoo dot com
13 years ago
while joogat's one line function is short, it is probably better to calculate factorial iteratively instead of recursively. keep in mind if you want large factorials, you'll need to use some sort of arbitrary precision integer or perhaps the BCMath functions. then again, unless you're trying to do large numbers (170! is the highest that you can do that does not return infinity) you probably won't notice any time difference.
<?php
function factorial(\$in) {

// 0! = 1! = 1

\$out = 1;

// Only if \$in is >= 2

for (\$i = 2; \$i <= \$in; \$i++) {

\$out *= \$i;
}

return
\$out;
}
?>
webkid%webkid.com
16 years ago
And the reason I needed a Factorial function is because I there were no nPr or nCr functions native to PHP, either.

function n_pick_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (fact(\$n)/fact(\$n-\$r));}
function n_choose_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (n_pick_r(\$n,\$r)/fact(\$r));}

Hope that helps someone!
-1
php at keith tyler dot com
7 years ago
Another ordinal method, which does not involve utilizing date functions:

<?php
sprintf
( "%d%s", \$t, array_pop( array_slice( array_merge( array( "th","st","nd","rd"), array_fill( 4,6,"th")), \$t%10, 1)));'
?>
-1
bjcffnet at gmail dot com
13 years ago
thearbitcouncil at gmail dot com, you could just use array_sum():
<?php
function average(\$arr)
{
if (!
is_array(\$arr)) return false;

return
array_sum(\$arr)/count(\$arr);
}

\$array = array(5, 10, 15);
echo
average(\$array); // 10
?>
-1
jerry dot wilborn at fast dot net
15 years ago
Here is how to calculate standard deviation in PHP where \$samples is an array of incrementing numeric keys and the values are your samples:

\$sample_count = count(\$samples);

for (\$current_sample = 0; \$sample_count > \$current_sample; ++\$current_sample) \$sample_square[\$current_sample] = pow(\$samples[\$current_sample], 2);

\$standard_deviation = sqrt(array_sum(\$sample_square) / \$sample_count - pow((array_sum(\$samples) / \$sample_count), 2));
-1
info at gavinvincent dot co dot uk
13 years ago
If you need to deal with polar co-ordinates for somereason you will need to convert to and from x,y for input and output in most situations: here are some functions to convert cartesian to polar and polar to cartesian
<?
//returns array of r, theta in the range of 0-2*pi (in radians)
function rect2polar(\$x,\$y)
{
if(is_numeric(\$x)&&is_numeric(\$y))
{
\$r=sqrt(pow(\$x,2)+pow(\$y,2));
if(\$x==0)
{
if(\$y>0) \$theta=pi()/2;
else \$theta=3*pi()/2;
}
else if(\$x<0) \$theta=atan(\$y/\$x)+pi();
else if(\$y<0) \$theta=atan(\$y/\$x)+2*pi();
else \$theta=atan(\$y/\$x);
\$polar=array("r"=>\$r,"theta"=>\$theta);
return \$polar;
}
else return false;
}

//r must be in radians, returns array of x,y
function polar2rect(\$r,\$theta)
{
if(is_numeric(\$r)&&is_numeric(\$theta))
{
\$x=\$r*cos(\$theta);
\$y=\$r*sin(\$theta);
\$rect=array("x"=>\$x,"y"=>\$y);
}
else
{
return false;
}
}
?>
-1
Florian
12 years ago
A function that simulates the sum operator. (http://en.wikipedia.org/wiki/Sum). Be careful with the expression because it may cause a security hole; note the single quotes to don't parse the "\$".
<?php
# @param    string    \$expr    expression to evaluate (for example (2*\$x)^2+1)
# @param    string    \$var      dummy variable (for example "x")
# @param    integer    \$start
# @param    integer    \$end
# @param    integer    \$step

function sum(\$expr,\$var,\$start,\$end,\$step = 1) {

\$expr = str_replace(';','',\$expr);

\$var = str_replace('\$','',\$var);

\$start = (int)\$start;    \$end = (int)\$end;    \$step = (int)\$step;    \$sum = 0;

for (
\$i = \$start; \$i <= \$end; \$i = \$i + \$step) {

\$_expr = str_replace('\$'.\$var,\$i,\$expr);

\$_eval = '\$_result = '.\$_expr.'; return \$_result;';

\$_result = eval(\$_eval);
if(
\$result === FALSE) return "SYNTAX ERROR : \$expr";

\$sum += \$_result;
}
return (int)
\$sum;
}
?>
-1
monte at ohrt dot com
12 years ago
This is an efficient method of calculating the binomial coefficient C(n,k). This code was derived from Owant: Mastering Algorithms with Perl.

<?php

// calculate binomial coefficient

function binomial_coeff(\$n, \$k) {

\$j = \$res = 1;

if(
\$k < 0 || \$k > \$n)
return
0;
if((
\$n - \$k) < \$k)

\$k = \$n - \$k;

while(
\$j <= \$k) {

\$res *= \$n--;

\$res /= \$j++;
}

return
\$res;

}
?>

If you compiled php with --enable-bcmath, you can get full integer values of extremely large numbers by replacing:

\$res *= \$n--;
\$res /= \$j++;

with:

\$res = bcmul(\$res, \$n--);
\$res = bcdiv(\$res, \$j++);
-2
capripot at gmail dot com
6 years ago
Another simpler function to check a number with the luhn algorithm :

<?php
function luhn(\$num){
if(!
\$num)
return
false;

\$num = array_reverse(str_split(\$num));

foreach(
\$num as \$k => \$v){
if(
\$k%2)

\$v = \$v*2;

\$add += (\$v >= 10 ? \$v - 9 : \$v);
}
return (
}
?>

Don't know if foreach and arrays operations are faster than while and substr, but I feel it clearer.
-2
edward at edwardsun dot com
12 years ago
well just a note.. maybe i'm a bit stupid.. but remember to use pow() rather than the "^" sign for exponents.. as it took me 5 minutes to figure out why it wasn't working.
-1
AsherMaximum gmail
7 years ago
Here's a simple way way to convert a number to an ordinal number I created:

\$i == the number to convert. Put this inside a for loop if you need to populate an array.

<?php
// change increment variable to ordinal number.
\$n1 = \$i % 100; //first remove all but the last two digits

\$n2 = (\$n1 < 20 ? \$1 : \$i % 10; //remove all but last digit unless the number is in the teens, which all should be 'th'

//\$n is now used to determine the suffix.
\$ord = (\$n2==1 ? \$i.'st' : ( (\$n2==2 ? \$i.'nd' : (\$n2==3 ? \$i.'rd' : \$i.'th') ) ) )
?>
-2
florian at shellfire dot de
14 years ago
Please note that shorter is not always better
(meaning that really short faculty implementation above).

In my opinion, a clearer way to code this is, including a check
for negative or non-integer values.

In order to calculate the faculty of a positive integer,
an iterative way (which might be harder to understand)
is usually a bit faster, but I am using it only for small
values so it is not really important to me:

<?php

// Calculate the Faculty of a positive int-value

function iFaculty(\$a_iFac)
{
if (
\$a_iFac > 0)
{
return
\$a_iFac * \$this->iFaculty(\$a_iFac - 1);
}
elseif (
\$a_iFac == 0)
{
return
1;
}
else
{
return
0// Wrong argument!

}
}
?>

I've also written another function to calculate the
binomial coefficient of 2 values, I didn't find it anywhere yet so I hope it might help someone (works fine with the above stated faculty-function and ready to be used inside of your own classes!)

<?php

// calculates the binomial coefficient "n over k" of 2 positive int values
// for n >= k

function iBinCoeff(\$a_iN, \$a_iK)
{

// the binomial coefficient is defined as n! / [ (n-k)! * k! ]

return \$this->iFaculty(\$a_iN) / (\$this->iFaculty(\$a_iN - \$a_iK) * \$this->iFaculty(\$a_iK));
}

?>
-1
jl85 at yahoo dot com
14 years ago
Here's yet another greatest common denominator (gcd) function, a reeeeally small one.

function gcd(\$n,\$m){
if(!\$m)return\$n;return gcd(\$m,\$n%\$m);
}

It works by recursion. Not really sure about it's speed, but it's really small! This won't work on floating point numbers accurately though. If you want a floating point one, you need to have at least PHP 4, and the code would be

function gcd(\$n,\$m){
if(!\$m)return\$n;return gcd(\$m,fmod(\$n,\$m));
}
-2
Mike
10 years ago
//had a mistake in last post, heres the corrected version

/*
Just a simple function to trim digits from the left side of an integer. TRIM DOWN TO 4-> (ie. 987654 => 7654)
*/

function trimInteger(\$targetNumber,\$newLength) {

\$digits = pow(10,\$newLength);

\$s = (\$targetNumber/ \$digits); //make the last X digits the                  decimal part

\$t = floor(\$targetNumber / \$digits); //drop the last X digits (the decimal part)

\$h = \$s - \$t; //remove all  but the decimal part

\$newInteger = (\$h*\$digits); //make the everything after the decimal point the new number

return \$newInteger;
}
-1
ian at mp3 dot com
17 years ago
for those looking for a credit card verification function i wrote a simple LUHN Formula algorithm:

<?php
\$valid
= 1;

\$numOfDigits = 0 - strlen(\$ccNumber);

\$i = -1;
while (
\$i>=\$numOfDigits){
if ((
\$i % 2) == 0){

\$double = 2*(substr(\$ccNumber, \$i, 1));

\$total += substr(\$double,0,1);
if (
strlen(\$double > 1)){

\$total += substr(\$double,1,1);
}
} else {

\$total += substr(\$ccNumber, \$i, 1);
}

\$i--;
}

if ((
\$total % 10) != 0){

\$valid = 0;
}
?>
-2
moikboy (nospam!) moikboy (nospam!) hu
12 years ago
I think, this is the optimal code for calculating factorials:

<?php
function fact(\$int){
if(
\$int<2)return 1;
for(
\$f=2;\$int-1>1;\$f*=\$int--);
return
\$f;
};
?>

And another one for calculating the \$int-th Fibonacci-number:

<?php
function fib(\$int){
static
\$fibTable=array();
return empty(
\$fibTable[\$int])?\$fibTable[\$int] = \$int>1?fib(\$int-2)+fib(\$int-1):1:\$fibTable[\$int];
};
?>
-2
help at gjbdesign dot com
13 years ago
Occasionally a user must enter a number in a form. This function converts fractions to decimals and leaves decimals untouched. Of course, you may wish to round the final output, but that is not included here.

<?php
/*Some example values of \$q
\$q = "2.5";
\$q = "2 1/2";
\$q = "5/2";
*/
function Deci_Con(\$q){
//check for a space, signifying a whole number with a fraction

if(strstr(\$q, ' ')){

\$wa = strrev(\$q);

\$wb = strrev(strstr(\$wa, ' '));

\$whole = true;//this is a whole number

}
//now check the fraction part

if(strstr(\$q, '/')){
if(
\$whole==true){//if whole number, then remove the whole number and space from the calculations

\$q = strstr(\$q, ' ');
}
\$b = str_replace("/","",strstr(\$q, '/'));//this is the divisor
//isolate the numerator
\$c = strrev(\$q);
\$d = strstr(\$c, '/');
\$e = strrev(\$d);
\$a = str_replace("/","",\$e);//the pre-final numerator

if(\$whole==true){//add the whole number to the calculations

\$a = \$a+(\$wb*\$b);//new numerator is whole number multiplied by denominator plus original numerator

}
\$q = \$a/\$b;//this is now your decimal
return \$q;
}else{
return
\$q;//not a fraction, just return the decimal

}
}
?>
-2
fabien_mornand at yahoo dot fr
14 years ago
here is an algorithm to calculate gcd of a number. This is Euclid algorithm i was studying in Maths. I've converted it in php for the fun.

<?php
if(\$a && \$b)
{
\$ax=\$a; \$bx=\$b;

\$r=fmod(\$a,\$b);
if(!
\$r){\$rx=\$r;}
while(
\$r){

\$rx=\$r;

\$a=\$b;

\$b=\$r;

\$r=fmod(\$a,\$b);
}
}
echo
'PGCD ('.\$ax.' , '.\$bx.' ) = '.\$rx;
?>
-1
Anonymous
7 months ago
And the reason I needed a Factorial function is because I there were no nPr or nCr functions native to PHP, either.

function n_pick_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (fact(\$n)/fact(\$n-\$r));}
function n_choose_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (n_pick_r(\$n,\$r)/fact(\$r));}

Hope that helps someone!
exmple:https://vb.3dlat.com/
-2
Aiden880
3 years ago
Lowest Common Denominator:
function lcd(\$num, \$start) {
while(\$num % \$start != 0) {
\$start++;
}
return \$start;
}
-2
Chronial "at" cyberpunkuniverse.de
14 years ago
Here are are a nPr and a nPc function
(had to define NaN - don't know, how to this the "rigth" way)

<?php
define
(NaN,acos(1.01));

function
nCr(\$n,\$r){
if (
\$r > \$n)
return
NaN;
if ((
\$n-\$r) < \$r)
return
nCr(\$n,(\$n-\$r));

\$return = 1;
for (
\$i=0;\$i < \$r;\$i++){

\$return *= (\$n-\$i)/(\$i+1);
}
return
\$return;
}

function
nPr(\$n,\$r){
if (
\$r > \$n)
return
NaN;
if (
\$r)
return
\$n*(nPr(\$n-1,\$r-1));
else
return
1;
}
?>
-2
jl85 at yahoo dot com
15 years ago
Theres another faster way of doing even/odd number checking by using bitwise operators. Don't ask me how it works, I just found this out by experimenting with it (could the editor possibly explain?)

if ((1&\$num)) {
echo "\$num is odd";
}

if (!(1&\$num)) {
echo "\$num is even";
}

How it works is (1&\$num) returns a 1 for odd numbers and returns 0 when it's an even number.
-2
patience at worldonline dot nl
16 years ago
The example for Factorials given above is wrong. Here a correct version, so that you do not have to reinvent the wheel again...

<?php
function mathFact( \$s )
{

\$r = (int) \$s;

if (
\$r < 2 )

\$r = 1;
else {
for (
\$i = \$r-1; \$i > 1; \$i-- )

\$r = \$r * \$i;
}

return(
\$r );
}
?>
-3
marasek.SPAMLESS at telton.de
12 years ago
I could not resist to do a simpler version of the ordinal function:
<?php
function ordinal(\$num)
{

\$num = (int)\$num;

\$digit = substr(\$num, -1, 1);

\$ord = "th";
switch(
\$digit)
{
case
1: \$ord = "st"; break;
case
2: \$ord = "nd"; break;
case
3: \$ord = "rd"; break;
break;
}
return
\$num.\$ord;
}
?>
One could replace the typecast with

<?php
if(\$num===NULL or \$num==="")
{return
NULL;}
?>

to get an empty result instead of "0th" in case \$num is empty too.
-4
thearbitcouncil at gmail dot com
13 years ago
Two functions I didn't find elsewhere... one to compute mean of an array of numbers, and another to computer variance of a sample of numbers. Both take an array of numbers as arguments. Not much error checking, or optimization...

(note: variance function uses the average function...)

<?php

function average(\$arr)
{
if (!
count(\$arr)) return 0;

\$sum = 0;
for (
\$i = 0; \$i < count(\$arr); \$i++)
{

\$sum += \$arr[\$i];
}

return
\$sum / count(\$arr);
}

function
variance(\$arr)
{
if (!
count(\$arr)) return 0;

\$mean = average(\$arr);

\$sos = 0;    // Sum of squares

for (\$i = 0; \$i < count(\$arr); \$i++)
{

\$sos += (\$arr[\$i] - \$mean) * (\$arr[\$i] - \$mean);
}

return
\$sos / (count(\$arr)-1);  // denominator = n-1; i.e. estimating based on sample
// n-1 is also what MS Excel takes by default in the
// VAR function
}

echo
variance(array(4,6,23,15,18)); // echoes 64.7...correct value :)

?>
-2
barry at megaspace dot com
11 years ago
Here's a least common denominator (lcd) function:

\$array = array(3,4,6,8,18,2);

function lcd(\$array,\$x) {

\$mod_sum = 0;

for(\$int=1;\$int < count(\$array);\$int++) {
\$modulus[\$int] = (\$array[0]*\$x) % (\$array[\$int]);
\$mod_sum = \$mod_sum + \$modulus[\$int];
}

if (!\$mod_sum) {
echo "LCD: ".(\$array[0]*\$x)."\n";
}

else {
lcd(\$array,\$x+1);
}

}

lcd(\$array,1);
-2
daniel at g-loc dot org
12 years ago
If you're an aviator and needs to calculate windcorrection angles and groundspeed (e.g. during flightplanning) this can be very useful.

You can probably write these lines more beautiful, but they work!
-2
jordanolsommer at imap dot cc
15 years ago
The reason the bitwise AND ("&") operator works to determine whether a number is odd or even is because odd numbers expressed in binary always have the rightmost (2^0) bit = 1 and even numbers always have the 2^0 bit = 0.

So if you do a " 1 & \$num", it will return zero if the number is even (since xxxxxxx0 [the even number in binary] and 00000001 [the 1]) don't share any bits, and will return 1 if the number is odd (xxxxxx1 and 000001).

a clever way of doing things, but \$num % 2 would work as well i think :).
-4
lummox
10 years ago
Wouldn't the following function do the same but a lot easier than the one in the comment before?

function trimInteger(\$targetNumber,\$newLength) {
return \$targetNumber%pow(10,\$newLength);
}
-3
tembenite at gmail dot com
11 years ago
To add to what Cornelius had, I have written a function that will take an array of numbers and return the least common multiple of them:

function lcm_arr(\$items){
//Input: An Array of numbers
//Output: The LCM of the numbers
while(2 <= count(\$items)){
array_push(\$items, lcm(array_shift(\$items), array_shift(\$items)));
}
return reset(\$items);
}

//His Code below with \$'s added for vars

function gcd(\$n, \$m) {
\$n=abs(\$n); \$m=abs(\$m);
if (\$n==0 and \$m==0)
return 1; //avoid infinite recursion
if (\$n==\$m and \$n>=1)
return \$n;
return \$m<\$n?gcd(\$n-\$m,\$n):gcd(\$n,\$m-\$n);
}

function lcm(\$n, \$m) {
return \$m * (\$n/gcd(\$n,\$m));
}
-2
ddarjany at yahoo dot com
11 years ago
Tim's fix of Evan's ordinal function causes another problem, it no longer works for number above 100.  (E.g. it returns 111st instead of 111th).
Here is a further modified version which should work for all numbers.

<?PHP

function ordinal(\$cardinal)    {

\$cardinal = (int)\$cardinal;

\$digit = substr(\$cardinal, -1, 1);

if (
\$cardinal <100) \$tens = round(\$cardinal/10);
else
\$tens = substr(\$cardinal, -2, 1);

if(
\$tens == 1)  {
return
\$cardinal.'th';
}

switch(
\$digit) {
case
1:
return
\$cardinal.'st';
case
2:
return
\$cardinal.'nd';
case
3:
return
\$cardinal.'rd';
default:
return
\$cardinal.'th';
}
}
?>
-2
15 years ago
Here is a cleaner factorial function:

function factorial(\$s){
if(\$s) \$r = \$s * factorial(\$s - 1);
else \$r = 1;
return \$r;
}
-2
jbeardsl at gte dot net
15 years ago
I needed a truncate function to operate on real numbers. I preferred not to use a string-manipulation method, so here's my solution. HTH...

function truncate (\$num, \$digits = 0) {

//provide the real number, and the number of
//digits right of the decimal you want to keep.

\$shift = pow(10 , \$digits);
return ((floor(\$num * \$shift)) / \$shift);

}
-4
twoscoopsofpig at NOSPAM dot gmail dot com
12 years ago
@ Moikboy:

This may or may not be more simplified factorialization:

<?php
\$f
=\$fact=25;
while (
\$fact>0)
{
\$f=\$f*\$fact--;}
echo
\$f;
?>
-4
graywh at gmail DELETE dot com
13 years ago
If you're really concerned about speed, you could compute the factorial of large numbers using the Gamma function of n-1.

Integral y^(t-1)*Exp(-y) for y from 0 to Infinity

For Fibonacci numbers, there's a better-than-recursive way.

((1+sqrt(5))/2)^(n/sqrt(5)) - ((1-sqrt(5))/2)^(n/sqrt(5))
-4
chris at free-source dot com
14 years ago
to "convert" scientific notation to a float simply cast it:
<?php
\$val
= '3.5e4';
\$val = (float) \$val;
echo
\$val;
?>

output:
35000
-4
cornelius at skjoldhoej dot dk
17 years ago
I found that when dealing with tables, a 'least common multiple' function is sometimes useful for abusing tablespan and the likes.

So here goes (you may choose to remove the first part of the gcd function if the function call is well-behaved):

<?php
function gcd(n, m) //greatest common divisor
{

n=abs(n); m=abs(m);
if (
n==0 and m==0)
return
1; //avoid infinite recursion

if (n==m and n>=1)
return
n;
return
m<n?gcd(n-m,n):gcd(n,m-n);
}

function
lcm(n, m) //least common multiple
{
return
m*(n/gcd(n,m));
}
?>

This may or may not be something to consider adding to the mathematical function library.
-7
eric at woolhiser dot com
13 years ago
For all you guys writing mortgage calculators out there:

<?php

function payment(\$apr,\$n,\$pv,\$fv=0.0,\$prec=2){

/* Calculates the monthly payment rouned to the nearest penny
** \$apr = the annual percentage rate of the loan.
** \$n   = number of monthly payments (360 for a 30year loan)
** \$pv    = present value or principal of the loan
** \$fv  = future value of the loan
** \$prec = the precision you wish rounded to
*/
/****************************************\
** No Warranty is expressed or implied. **
*****************************************/

if (\$apr !=0) {

\$alpha = 1/(1+\$apr/12);

\$retval round(\$pv * (1 - \$alpha) / \$alpha /
(
1 - pow(\$alpha,\$n)),\$prec) ;
} else {

\$retval = round(\$pv / \$n, \$prec);
}
return(
\$retval);

}
?>
-4
erikvandeven100 at gmail dot com
1 year ago
This is my factorial method
<?php
function factorial(\$nr)
{

\$product = array_product(range(1,++\$nr));
return
\$product / \$nr;
}
?>
It uses the reversed method by applying division instead of multiplication, so it even returns the right answer when entering 0.
-5
jos at gtacrime dot nl
12 years ago
Thanks to Chronial "at" cyberpunkuniverse.de, I was able to create the binompdf(n, p, k) function.

<?php
function nCr(\$n, \$k){
if (
\$k > \$n)
return
NaN;
if ((
\$n - \$k) < \$k)
return
nCr(\$n, (\$n - \$k));

\$return = 1;
for (
\$i=0; \$i<\$k; \$i++){

\$return *= (\$n - \$i) / (\$i + 1);
}
return
\$return;
}

function
binompdf(\$n, \$p, \$k){

\$return = nCr(\$n, \$k) * pow(\$p, \$k) * pow((1 - \$p), (\$n - \$k));
return
\$return;
}
?>
-5
donnieb819 at hotmail dot NOSPAM dot com
14 years ago
Method to convert an arbitrary decimal number to its most reduced fraction form (so a string is returned, this method would probably be used for output formatting purposes.)  There were other methods similar to this one on the page, but none did quite what I wanted.  It's maybe not the most elegant code, but it gets the job done.  Hope this helps someone.  An iterative form of Euclid's algorithm is used to find the GCD.

<?php
function dec2frac( \$decimal )
{

\$decimal = (string)\$decimal;

\$num = '';

\$den = 1;

\$dec = false;

// find least reduced fractional form of number

for( \$i = 0, \$ix = strlen( \$decimal ); \$i < \$ix; \$i++ )
{

// build the denominator as we 'shift' the decimal to the right

if( \$dec ) \$den *= 10;

// find the decimal place/ build the numberator

if( \$decimal{\$i} == '.' ) \$dec = true;
else
\$num .= \$decimal{\$i};
}

\$num = (int)\$num;

// whole number, just return it

if( \$den == 1 ) return \$num;

\$num2 = \$num;

\$den2 = \$den;

\$rem  = 1;

// Euclid's Algorithm (to find the gcd)

while( \$num2 % \$den2 ) {

\$rem = \$num2 % \$den2;

\$num2 = \$den2;

\$den2 = \$rem;
}
if(
\$den2 != \$den ) \$rem = \$den2;

// now \$rem holds the gcd of the numerator and denominator of our fraction

return (\$num / \$rem ) . "/" . (\$den / \$rem);
}
?>

Examples:
echo dec2frac( 10 );
echo dec2frac( .5 );
echo dec2frac( 5.25 );
echo dec2frac( .333333333 );

yields:
10
1/2
21/4
333333333/1000000000
-4
tim at durge dot org
11 years ago
In Evan's ordinal function, the line:

<?php
\$tens
= substr(\$cardinal, -2, 1);
?>

needs to be replaced by:

<?php
\$tens
= round(\$cardinal/10);
?>

or similar. At least on PHP 4.3.10,  substr("1", -2, 1)  returns '1' - so Evan's function gives "1th", as well as "11th".  This is contrary to the documentation, but is noted in the comments on the substr manual page.
-4
ausvald at tut dot by
14 years ago
I see there are some factorial functions below.

I'll provide the best one:

<?
function factorial(\$n){ \$n=(int)\$n;
\$f=1;
for(;\$n>0;--\$n) \$f*=\$n;
return \$f;
}
?>
-5
rubo77 at spacetrace dot org
10 years ago
<?php
function lcd(\$n,\$m, \$maxvarianzpercent=0){

// set \$maxvarianzpercent=5 to get a small, but approx. result
/* a better lcd function with varianz:
for example use
lcd(141,180,5) to get the approx. lcd '7/9' which is in fact 140/180
*/
// ATTENTION!!! can be really slow if \$m is >1000

\$d=\$n/\$m;

\$f=1;
while(
\$d*\$f!=intval(\$d*\$f)){

\$f++;
}

\$r=(\$d*\$f).'/'.\$f;
if((
\$d*\$f)<=10 or \$f<=10) return \$r;
else if(
\$maxvarianzpercent>0){

\$f=1;
while(
\$d*\$f!=intval(\$d*\$f) and (\$d*\$f)-intval(\$d*\$f) > \$maxvarianzpercent/100){

\$f++;
}
return
intval(\$d*\$f).'/'.\$f;
} else return
\$r;
}
?>
-5
Evan Broder
12 years ago
A slightly more complex but much more accurate cardinal=>ordinal function (the one below doesn't account for 11th, 12th, and 13th, which don't follow the usual rules):

<?php

function ordinal(\$cardinal)
{

\$cardinal = (int)\$cardinal;

\$digit = substr(\$cardinal, -1, 1);

\$tens = substr(\$cardinal, -2, 1);
if(
\$tens == 1)
{
return
\$cardinal.'th';
}

switch(
\$digit)
{
case
1:
return
\$cardinal.'st';
case
2:
return
\$cardinal.'nd';
case
3:
return
\$cardinal.'rd';
default:
return
\$cardinal.'th';
}
}

?>
-5
shanx at shanx dot com
16 years ago
<?

/**
* Function to calculate base36 values from a number. Very
* useful if you wish to generate IDs from numbers.
*
* @param \$value The number
* @param \$base The base to be applied (16, 36 or 64)
* @return The calculated string
* @author Shashank Tripathi (shanx@shanx.com)
* @version 0.1 - Let me know if something doesnt work
*
*/

function base36(\$value, \$base)
{
\$baseChars = array('0', '1', '2', '3', '4', '5',
'6', '7', '8', '9', 'a', 'b',
'c', 'd', 'e', 'f', 'g', 'h',
'i', 'j', 'k', 'l', 'm', 'n',
'o', 'p', 'q', 'r', 's', 't',
'u', 'v', 'w', 'x', 'y', 'z'
);

\$remainder = 0;
\$newval = "";

while ( \$value > 0 )
{
\$remainder = \$value % \$base;
\$value = ( (\$value - \$remainder)/ \$base );
\$newval .= \$baseChars[\$remainder];
}
return strrev(\$newval);

}

echo "The string for 46655, for instance, is " . base36(46655, 36);

?>
-7
webkid%webkid.com
16 years ago
I found it kind of irritating that PHP had no native functionality for a calculating Factorials. Since I really didn't feel like loading the GMP library, I figured I'd write my own function.

function fact(\$s){\$r=(int)\$s; for (\$i=\$r;\$i--;\$i>1){\$r=\$r*\$i;} return \$r;}

I think that's right... I havn't tested it extensively but it should work.