Floating-point cheat sheet for PHP
Floating-Point Types
PHP is dynamically typed and will often convert implicitly between strings and floating-point numbers (which are platform-dependant, but typically IEEE 64 bit values). To force a value to floating-point, cast it:
$foo = (float)'10.5';
Decimal Types
The BC Math and Decimal extensions implement arbitrary-precision decimal math:
$a = '0.1';
$b = '0.2';
echo bcadd($a, $b); // prints 0.3
$a = new Decimal('0.1');
$b = new Decimal('0.2');
echo $a + $b; // prints 0.3
How to Round
Rounding can be done with the number_format() function:
$number = 4.123;
echo number_format($number, 2); // prints 4.12
If you are using the decimal extension, you can round using the round method:
$decimal = new Decimal("4.123");
echo $decimal->round(2); // prints 4.12
Resources
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