Compare floats in php

Question

I want to compare two floats in PHP, like in this sample code:

$a = 0.17;
$b = 1 - 0.83; //0.17
if($a == $b ){
 echo \'a and b are same\';
}
else {
 echo \'a         


        

Answer 1

Here is a useful class from my personal library for dealing with floating point numbers. You can tweek it to your liking and insert any solution you like into the class methods :-).

/**
 * A class for dealing with PHP floating point values.
 * 
 * @author Anthony E. Rutledge
 * @version 12-06-2018
 */
final class Float extends Number
{
    // PHP 7.4 allows for property type hints!

    private const LESS_THAN = -1;
    private const EQUAL = 0;
    private const GREATER_THAN = 1;

    public function __construct()
    {

    }

    /**
     * Determines if a value is an float.
     * 
     * @param mixed $value
     * @return bool
     */
    public function isFloat($value): bool
    {
        return is_float($value);
    }

    /**
     * A method that tests to see if two float values are equal.
     * 
     * @param float $y1
     * @param float $y2
     * @return bool
     */
    public function equals(float $y1, float $y2): bool
    {
        return (string) $y1 === (string) $y2;
    }

    /**
     * A method that tests to see if two float values are not equal.
     * 
     * @param float $y1
     * @param float $y2
     * @return bool
     */
    public function isNotEqual(float $y1, float $y2): bool
    {
        return !$this->equals($y1, $y2);
    }

    /**
     * Gets the bccomp result.
     * 
     * @param float $y1
     * @param float $y2
     * @return int
     */
    private function getBccompResult(float $y1, float $y2): int
    {
        $leftOperand = (string) $y1;
        $rightOperand = (string) $y2;

        // You should check the format of the float before using it.

        return bccomp($leftOperand, $rightOperand);
    }

    /**
     * A method that tests to see if y1 is less than y2.
     * 
     * @param float $y1
     * @param float $y2
     * @return bool
     */
    public function isLess(float $y1, float $y2): bool
    {
        return ($this->getBccompResult($y1, $y2) === self::LESS_THAN);
    }

    /**
     * A method that tests to see if y1 is less than or equal to y2.
     * 
     * @param float $y1
     * @param float $y2
     * @return bool
     */
    public function isLessOrEqual(float $y1, float $y2): bool
    {
        $bccompResult = $this->getBccompResult($y1, $y2);
        return ($bccompResult === self::LESS_THAN || $bccompResult === self::EQUALS);
    }

    /**
     * A method that tests to see if y1 is greater than y2.
     * 
     * @param float $y1
     * @param float $y2
     * @return bool
     */
    public function isGreater(float $y1, float $y2): bool
    {
        return ($this->getBccompResult($y1, $y2) === self::GREATER_THAN);
    }

    /**
     * A method that tests to see if y1 is greater than or equal to y2.
     * 
     * @param float $y1
     * @param float $y2
     * @return bool
     */
    public function isGreaterOrEqual(float $y1, float $y2): bool
    {
        $bccompResult = $this->getBccompResult($y1, $y2);
        return ($bccompResult === self::GREATER_THAN || $bccompResult === self::EQUALS);
    }

    /**
     * Returns a valid PHP float value, casting if necessary.
     * 
     * @param mixed $value
     * @return float
     *
     * @throws InvalidArgumentException
     * @throws UnexpectedValueException
     */
    public function getFloat($value): float
    {
        if (! (is_string($value) || is_int($value) || is_bool($value))) {
            throw new InvalidArgumentException("$value should not be converted to float!");
        }

        if ($this->isFloat($value)) {
            return $value;
        }

        $newValue = (float) $value;

        if ($this->isNan($newValue)) {
            throw new UnexpectedValueException("The value $value was converted to NaN!");
        }

        if (!$this->isNumber($newValue)) {
            throw new UnexpectedValueException("The value $value was converted to something non-numeric!");
        }

        if (!$this->isFLoat($newValue)) {
            throw new UnexpectedValueException("The value $value was not converted to a floating point value!");
        }

        return $newValue;
    }
}
?>