Cara menggunakan php json_encode float precision

This library provides a PHP extension that adds support for correctly-rounded, arbitrary-precision decimal floating point arithmetic. Applications that rely on accurate numbers (ie. money, measurements, or mathematics) can use

pecl install decimal

pecl install decimal

pecl install decimal

The implementation uses the same arbitrary precision library as Python’s decimal, called mpdecimal.

The decimal extension offers several advantages over the

pecl install decimal

• All rational numbers can be represented accurately. In contrast, numbers like

  pecl install decimal
  

  4 do not have exact representations in binary floating point. You can read more about this in the floating point guide or in PHP’s documentation.
• While a binary floating point value like

  pecl install decimal
  

  4 comes close, the small difference prevents reliable equality testing, and inaccuracies may accumulate over time.
• Arbitrary precision allows for numbers that are not bound by the same upper and lower limits as

  pecl install decimal
  

  1 - numbers can be as big or small as required.
• PHP does a good job of hiding the inaccuracies of binary floating point representation with the INI setting. By default,

  pecl install decimal
  

  7 will have a string value of

  pecl install decimal
  

  8 even though the internal C

  pecl install decimal
  

  9 can not represent the result accurately. For example:

var_dump(0.1 + 0.2);        // float(0.3)
var_dump(0.1 + 0.2 - 0.3);  // float(5.5511151231258E-17)

PHP already has arbitrary precision math functions…

The current goto answer for arbitrary precision math in PHP is bcmath. However, the

pecl install decimal

• Decimal values are objects, so you can typehint

  pecl install decimal
  

  0 instead of

  pecl install decimal
  

  2.
• Arithmetic and comparison operators are supported.
• Precision is defined as the number of significant figures, and scale is the number of digits behind the decimal point. This means that a number like

  phpbrew ext install decimal
  phpbrew ext enable  decimal
  

  3 would require a scale of

  phpbrew ext install decimal
  phpbrew ext enable  decimal
  

  4 but a precision of

  phpbrew ext install decimal
  phpbrew ext enable  decimal
  

  5. This library uses precision; bcmath uses scale.
• Scientific notation is supported, so you can use strings like

  phpbrew ext install decimal
  phpbrew ext enable  decimal
  

  6 to construct a

  pecl install decimal
  

  0. At the time of this writing, you can not do this with bcmath.
• Calculations are significantly faster. See for some benchmarks.

Installation

Dependencies

• PHP 7
• libmpdec 2.4+

Composer

Composer can not be used to install the extension. The

phpbrew ext install decimal
phpbrew ext enable  decimal

phpbrew ext install decimal
phpbrew ext enable  decimal

Install

The easiest way to install the extension is to use PECL:

pecl install decimal

If you are using phpbrew:

phpbrew ext install decimal
phpbrew ext enable  decimal

Enable

Remember to enable to extension in your .ini file.

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

Verify

You can confirm that the extension is installed with

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

Basic Usage

The

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

Special

pecl install decimal

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

use Decimal\Decimal;

$a = new Decimal("1", 2);
$b = new Decimal("7", 8);

print_r($a / $b);

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

Projects using this extension should avoid

pecl install decimal

use Decimal\Decimal;

$a = new Decimal("1", 2);
$b = new Decimal("7", 8);

print_r($a / $b);

pecl install decimal

pecl install decimal

JSON conversions will automatically convert the decimal to

pecl install decimal

A warning will be raised if value was not parsed completely. For example,

Decimal\Decimal Object
(
    [value] => 0.14285714
    [precision] => 8
)

Decimal\Decimal Object
(
    [value] => 0.14285714
    [precision] => 8
)

Decimal\Decimal Object
(
    [value] => 0.14285714
    [precision] => 8
)

Decimal\Decimal Object
(
    [value] => 0.14285714
    [precision] => 8
)

Decimal\Decimal Object
(
    [value] => 0.14285714
    [precision] => 8
)

Decimal\Decimal Object
(
    [value] => 0.14285714
    [precision] => 8
)

pecl install decimal

pecl install decimal

Decimal\Decimal Object
(
    [value] => 0.14285714
    [precision] => 8
)

For example:

use Decimal\Decimal;

$a = new Decimal("1", 2);
$b = new Decimal("7", 8);

print_r($a / $b);

Decimal\Decimal Object
(
    [value] => 0.14285714
    [precision] => 8
)

Scalar operands inherit the precision of the

pecl install decimal

pecl install decimal

pecl install decimal

For example:

use Decimal\Decimal;

$op1 = new Decimal("0.1", 4);
$op2 = "0.123456789";

print_r($op1 + $op2);


use Decimal\Decimal;

/**
 * @param int $n The factorial to calculate, ie. $n!
 * @param int $p The precision to calculate the factorial to.
 *
 * @return Decimal
 */
function factorial(int $n, int $p = Decimal::DEFAULT_PRECISION): Decimal
{
    return $n < 2 ? new Decimal($n, $p) : $n * factorial($n - 1, $p);
}

echo factorial(10000, 32);

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

Sandbox

This is a limited environment where you can experiment with

pecl install decimal

<?php use Decimal\Decimal; $a = new Decimal("0.1"); $b = new Decimal("7.0"); echo $a / $b;

Run Example Reset

Performance

The benchmark performs calculations on

pecl install decimal

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

It is difficult to determine what to use for the scale of bcmath, because it specifies the number of places behind the decimal point, rather than the precision, which is the total number of significant places. This benchmark is therefore arbitrary in itself and serves only to provide a rough idea of what to expect.

The code for this basic benchmark can be found here.

Results are the total runtime to produce a result across many iterations, in seconds. Lower is better.

Results

use Decimal\Decimal;

$op1 = new Decimal("0.1", 4);
$op2 = "0.123456789";

print_r($op1 + $op2);


use Decimal\Decimal;

/**
 * @param int $n The factorial to calculate, ie. $n!
 * @param int $p The precision to calculate the factorial to.
 *
 * @return Decimal
 */
function factorial(int $n, int $p = Decimal::DEFAULT_PRECISION): Decimal
{
    return $n < 2 ? new Decimal($n, $p) : $n * factorial($n - 1, $p);
}

echo factorial(10000, 32);

pecl install decimal

use Decimal\Decimal;

$op1 = new Decimal("0.1", 4);
$op2 = "0.123456789";

print_r($op1 + $op2);


use Decimal\Decimal;

/**
 * @param int $n The factorial to calculate, ie. $n!
 * @param int $p The precision to calculate the factorial to.
 *
 * @return Decimal
 */
function factorial(int $n, int $p = Decimal::DEFAULT_PRECISION): Decimal
{
    return $n < 2 ? new Decimal($n, $p) : $n * factorial($n - 1, $p);
}

echo factorial(10000, 32);

use Decimal\Decimal;

$op1 = new Decimal("0.1", 4);
$op2 = "0.123456789";

print_r($op1 + $op2);


use Decimal\Decimal;

/**
 * @param int $n The factorial to calculate, ie. $n!
 * @param int $p The precision to calculate the factorial to.
 *
 * @return Decimal
 */
function factorial(int $n, int $p = Decimal::DEFAULT_PRECISION): Decimal
{
    return $n < 2 ? new Decimal($n, $p) : $n * factorial($n - 1, $p);
}

echo factorial(10000, 32);

use Decimal\Decimal;

$op1 = new Decimal("0.1", 4);
$op2 = "0.123456789";

print_r($op1 + $op2);


use Decimal\Decimal;

/**
 * @param int $n The factorial to calculate, ie. $n!
 * @param int $p The precision to calculate the factorial to.
 *
 * @return Decimal
 */
function factorial(int $n, int $p = Decimal::DEFAULT_PRECISION): Decimal
{
    return $n < 2 ? new Decimal($n, $p) : $n * factorial($n - 1, $p);
}

echo factorial(10000, 32);

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

pecl install decimal

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

use Decimal\Decimal;

$op1 = new Decimal("0.1", 4);
$op2 = "0.123456789";

print_r($op1 + $op2);


use Decimal\Decimal;

/**
 * @param int $n The factorial to calculate, ie. $n!
 * @param int $p The precision to calculate the factorial to.
 *
 * @return Decimal
 */
function factorial(int $n, int $p = Decimal::DEFAULT_PRECISION): Decimal
{
    return $n < 2 ? new Decimal($n, $p) : $n * factorial($n - 1, $p);
}

echo factorial(10000, 32);

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

Warning: Loss of data on string conversion in ... on line 1
Decimal\Decimal Object
(
    [value] => 0.2235
    [precision] => 4
)

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

Attributes

Precision

Precision defines the number of significant figures that a decimal is accurate to. For example, a number like

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

use Decimal\Decimal;

(bool)   new Decimal();      // true, by convention
(bool)   new Decimal(1);     // true
(int)    new Decimal("1.5"); // 1
(float)  new Decimal("1.5"); // 1.5
(string) new Decimal("1.5"); // 1.5

pecl install decimal

use Decimal\Decimal;

(bool)   new Decimal();      // true, by convention
(bool)   new Decimal(1);     // true
(int)    new Decimal("1.5"); // 1
(float)  new Decimal("1.5"); // 1.5
(string) new Decimal("1.5"); // 1.5

use Decimal\Decimal;

(bool)   new Decimal();      // true, by convention
(bool)   new Decimal(1);     // true
(int)    new Decimal("1.5"); // 1
(float)  new Decimal("1.5"); // 1.5
(string) new Decimal("1.5"); // 1.5

Decimal operations, casting and construction will always preserve precision to avoid data loss:

• You can’t reduce the precision of a decimal.
• You can’t change the value of a decimal after it has been calculated.
• Constructing a decimal using a decimal will preserve the given decimal’s precision.

For example:

$a = new Decimal("0.1", 50);

$b = new Decimal($a);     // Precision is 50
$c = new Decimal($b, 6);  // Precision is 50
$d = new Decimal($c, 64); // Precision is 64

Arithmetic operations will result in a new decimal using the maximum precision of all operands. The developer’s only responsibility is to define the precision (as a minimum) when constructing a decimal. For example, if you have a

use Decimal\Decimal;

(bool)   new Decimal();      // true, by convention
(bool)   new Decimal(1);     // true
(int)    new Decimal("1.5"); // 1
(float)  new Decimal("1.5"); // 1.5
(string) new Decimal("1.5"); // 1.5

use Decimal\Decimal;

(bool)   new Decimal();      // true, by convention
(bool)   new Decimal(1);     // true
(int)    new Decimal("1.5"); // 1
(float)  new Decimal("1.5"); // 1.5
(string) new Decimal("1.5"); // 1.5

There are three precision constants:

• use Decimal\Decimal;
  
  (bool)   new Decimal();      // true, by convention
  (bool)   new Decimal(1);     // true
  (int)    new Decimal("1.5"); // 1
  (float)  new Decimal("1.5"); // 1.5
  (string) new Decimal("1.5"); // 1.5
  

  6

• use Decimal\Decimal;
  
  (bool)   new Decimal();      // true, by convention
  (bool)   new Decimal(1);     // true
  (int)    new Decimal("1.5"); // 1
  (float)  new Decimal("1.5"); // 1.5
  (string) new Decimal("1.5"); // 1.5
  

  7

• use Decimal\Decimal;
  
  (bool)   new Decimal();      // true, by convention
  (bool)   new Decimal(1);     // true
  (int)    new Decimal("1.5"); // 1
  (float)  new Decimal("1.5"); // 1.5
  (string) new Decimal("1.5"); // 1.5
  

  8

->precision(): int

Returns: 

int, the precision of this decimal.

Special Numbers

There are 3 special numbers:

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

use Decimal\Decimal;

$a = new Decimal("1", 2);
$b = new Decimal("7", 8);

print_r($a / $b);

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

pecl install decimal

pecl install decimal

->isNaN(): bool

Returns: 

bool,

pecl install decimal

->isInf(): bool

Returns: 

bool,

pecl install decimal

pecl install decimal

Integers

->isInteger(): bool

Returns: 

bool,

pecl install decimal

pecl install decimal

->isZero(): bool

Returns: 

bool,

pecl install decimal

Sign

->abs(): Decimal

Returns: 

Decimal, the absolute (positive) value of this decimal.

->negate(): Decimal

Returns: 

Decimal, the same value as this decimal, but the sign inverted.

->signum(): int

Returns: 

int,

pecl install decimal

pecl install decimal

pecl install decimal

->isPositive(): bool

Returns: 

bool,

pecl install decimal

pecl install decimal

->isNegative(): bool

Returns: 

bool,

pecl install decimal

pecl install decimal

Parity

->parity(): int

Returns: 

int,

pecl install decimal

pecl install decimal

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

pecl install decimal

->isEven(): bool

Returns: 

bool,

pecl install decimal

pecl install decimal

->isOdd(): bool

Returns: 

bool,

pecl install decimal

pecl install decimal

Rounding

The default rounding mode defined as

pecl install decimal

The reason for this default is to prevent biasing the average upwards or downwards.

This stack exchange answer provides some great examples for further reading.

Rounding Modes

The default rounding mode can not be changed because it affects how values are reduced to a precision. With a fixed internal rounding mode, an input value will always result in the same decimal value for a given precision, regardless of the environment. However, some methods allow you to provide a rounding mode, which can be any of the following constants:

• pecl install decimal
  

  27 (away from from)

• pecl install decimal
  

  28 (towards zero)

• pecl install decimal
  

  29 (towards positive infinity)

• pecl install decimal
  

  30 (towards negative infinity)

• pecl install decimal
  

  31 (halfway ties away from zero)

• pecl install decimal
  

  32 (halfway ties towards zero)

• pecl install decimal
  

  33 (halfway ties to nearest even number)

• pecl install decimal
  

  34 (halfway ties to nearest odd number)

• pecl install decimal
  

  35 (no rounding)

You can also use the corresponding PHP constants.

Rounding Methods

->floor(): Decimal

Returns: 

Decimal, the closest integer towards negative infinity.

->ceil(): Decimal

Returns: 

Decimal, the closest integer towards positive infinity.

->truncate(): Decimal

Returns: 

Decimal, the result of discarding all digits behind the decimal point.

->round(int $places = 0, int $mode = Decimal::ROUND_HALF_EVEN): Decimal

Returns: 

Decimal, the value of this decimal with the same precision, rounded according to the specified number of decimal places and rounding mode.

Throws:

• pecl install decimal
  

  36 if the rounding mode is not supported.

->trim(): Decimal

Returns: 

Decimal, a copy of this decimal without trailing zeroes.

Since:

1.1.0

->toFixed(int $places = 0, bool $commas = false, int $mode = Decimal::ROUND_HALF_EVEN): string

Returns: 

string, the value of this decimal formatted to a fixed number of decimal places, with thousands comma-separated, using a given rounding mode.

Comparing

Decimal objects are equal if their numeric values are equal, as well as their precision. The only value that breaks this rule is

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

Decimal objects can be compared to any other type to determine equality or relative ordering. Non-decimal values will be converted to decimal first (using the maximum precision). In cases where the type is not supported or comparison is not defined (eg. a decimal compared to

pecl install decimal

While decimal objects can not be constructed from a non-special

pecl install decimal

pecl install decimal

Decimal objects follow the standard PHP object conventions:

• Always

  pecl install decimal
  

  41.
• Always greater than

  pecl install decimal
  

  42.
• Identical (

  pecl install decimal
  

  43) if they are the same object, even if equal.

There are two methods that you can use to compare:

->equals(mixed $other): bool

This method is equivalent to the

pecl install decimal

Returns: 

bool,

pecl install decimal

->compareTo(mixed $other): int

This method is equivalent to the

pecl install decimal

Returns: 

int,

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

Operators

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

Converting

Decimal objects can be converted to

pecl install decimal

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

pecl install decimal

->toInt(): int

This method is equivalent to a cast to int.

Returns: 

int, the integer value of this decimal.

Throws:

• pecl install decimal
  

  65 if the value is greater than

  pecl install decimal
  

  66.

->toFloat(): float

This method is equivalent to a cast to float, and is not affected by the 'precision' INI setting.

Returns: 

float, the native PHP floating point value of this decimal.

Throws:

• pecl install decimal
  

  65 if the value is greater than

  pecl install decimal
  

  68.

• pecl install decimal
  

  69 if the value is smaller than

  pecl install decimal
  

  70.

->toString(): string

This method is equivalent to a cast to string.

Returns: 

string, the value of this decimal represented exactly, in either fixed or scientific form, depending on the value.

Casting

You can also cast a decimal to

pecl install decimal

pecl install decimal

extension=decimal.so        # Unix, OS X
extension=php_decimal.dll   # Windows

pecl install decimal

use Decimal\Decimal;

(bool)   new Decimal();      // true, by convention
(bool)   new Decimal(1);     // true
(int)    new Decimal("1.5"); // 1
(float)  new Decimal("1.5"); // 1.5
(string) new Decimal("1.5"); // 1.5

Important:

pecl install decimal

pecl install decimal

pecl install decimal

pecl install decimal

Arithmetic

Methods

->add(Decimal|string|int $value): Decimal

This method is equivalent to the

pecl install decimal

Returns: 

Decimal, the result of adding this decimal to the given value.

Throws:

• pecl install decimal
  

  80 if the value is not a decimal, string or integer.

->sub(Decimal|string|int $value): Decimal

This method is equivalent to the

pecl install decimal

Returns: 

Decimal, the result of subtracting a given value from this decimal.

Throws:

• pecl install decimal
  

  80 if the value is not a decimal, string or integer.

->mul(Decimal|string|int $value): Decimal

This method is equivalent to the

pecl install decimal

Returns: 

Decimal, the result of multiplying this decimal by the given value.

Throws:

• pecl install decimal
  

  80 if the given value is not a decimal, string or integer.

->div(Decimal|string|int $value): Decimal

This method is equivalent to the

pecl install decimal

Returns: 

Decimal, the result of dividing this decimal by the given value.

Throws:

• pecl install decimal
  

  80 if the value is not a decimal, string or integer.

• pecl install decimal
  

  87 if dividing by zero.

• pecl install decimal
  

  88 if division is undefined, eg.

  extension=decimal.so        # Unix, OS X
  extension=php_decimal.dll   # Windows
  

  9 / -

  extension=decimal.so        # Unix, OS X
  extension=php_decimal.dll   # Windows
  

  9

->mod(Decimal|string|int $value): Decimal

This method is equivalent to the

pecl install decimal

Returns: 

Decimal, the remainder after dividing the integer value of this decimal by the integer value of the given value.

Throws:

• pecl install decimal
  

  80 if the value is not a decimal, string or integer.

• pecl install decimal
  

  87 if the integer value of $value is zero.

• pecl install decimal
  

  88 if the operation is undefined, eg.

  extension=decimal.so        # Unix, OS X
  extension=php_decimal.dll   # Windows
  

  9 % -

  extension=decimal.so        # Unix, OS X
  extension=php_decimal.dll   # Windows
  

  9

->rem(Decimal|string|int $value): Decimal

Returns: 

Decimal, the remainder after dividing this decimal by a given value.

Throws:

• pecl install decimal
  

  80 if the value is not a decimal, string or integer.

• pecl install decimal
  

  87 if the integer value of $value is zero.

• pecl install decimal
  

  88 if the operation is undefined, eg.

  extension=decimal.so        # Unix, OS X
  extension=php_decimal.dll   # Windows
  

  9, -

  extension=decimal.so        # Unix, OS X
  extension=php_decimal.dll   # Windows
  

  9

->pow(Decimal|string|int $exponent): Decimal

This method is equivalent to the

phpbrew ext install decimal
phpbrew ext enable  decimal

Returns: 

Decimal, the result of raising this decimal to a given power.

Throws:

• pecl install decimal
  

  80 if the exponent is not a decimal, string or integer.

->shift(int $places): Decimal

Returns: 

Decimal, A copy of this decimal with its decimal place shifted.

->ln(): Decimal

This method is equivalent in function to PHP's

phpbrew ext install decimal
phpbrew ext enable  decimal

Returns: 

Decimal, the natural logarithm of this decimal (log base e), with the same precision as this decimal.

->exp(): Decimal

Returns: 

Decimal, the exponent of this decimal, ie. e to the power of this, with the same precision as this decimal.

->log10(): Decimal

Returns: 

Decimal, the base-10 logarithm of this decimal, with the same precision as this decimal.

->sqrt(): Decimal

Returns: 

Decimal, the square root of this decimal, with the same precision as this decimal.

Decimal::sum(array|Traversable $values, int $precision = 28): Decimal

The precision of the result will be the max of all precisions that were encountered during the calculation. The given precision should therefore be considered the minimum precision of the result. This method is equivalent to adding each value individually, then dividing by the number of values.