Do simple reliable math calculations without the risk of wrong results using bcmath

bccalc.php

<?php
/**
 * Do simple reliable floating point calculations without the risk of wrong results.
 *
 * @see http://floating-point-gui.de/
 * @see the big red warning on http://php.net/language.types.float.php
 *
 * In the rare case that the bcmath extension would not be loaded, it will return the
 * normal calculation results.
 *
 * @see Source: https://gist.github.com/jrfnl/8449978
 *
 * @param   mixed   $number1   Scalar (string/int/float/bool).
 * @param   string  $action    Calculation action to execute. Valid input:
 *                               '+' or 'add' or 'addition',
 *                               '-' or 'sub' or 'subtract',
 *                               '*' or 'mul' or 'multiply',
 *                               '/' or 'div' or 'divide',
 *                               '%' or 'mod' or 'modulus',
 *                               '=' or 'comp' or 'compare'.
 * @param   mixed   $number2	Scalar (string/int/float/bool).
 * @param   bool    $round      Whether or not to round the result. Defaults to false.
 *                              Will be disregarded for a compare operation.
 * @param   int     $decimals   Decimals for rounding operation. Defaults to 0.
 * @param   int     $precision  Calculation precision. Defaults to 10.
 *
 * @return int|float|false Calculation result or false if either of the numbers isn't scalar or
 *                         an invalid operation was passed.
 *                         - for compare the result will always be an integer.
 *                         - for all other operations, the result will either be an integer (preferred)
 *                           or a float.
 */
function bc_calc( $number1, $action, $number2, $round = false, $decimals = 0, $precision = 10 ) {
	if ( ! is_scalar( $number1 ) || ! is_scalar( $number2 ) ) {
		return false;
	}

	$bc = extension_loaded( 'bcmath' );

	if ( $bc ) {
		$number1 = number_format( $number1, 10, '.', '' );
		$number2 = number_format( $number2, 10, '.', '' );
	}

	$result  = null;
	$compare = false;

	switch ( $action ) {
		case '+':
		case 'add':
		case 'addition':
			$result = ( $bc ) ? bcadd( $number1, $number2, $precision ) /* string */ : ( $number1 + $number2 );
			break;

		case '-':
		case 'sub':
		case 'subtract':
			$result = ( $bc ) ? bcsub( $number1, $number2, $precision ) /* string */ : ( $number1 - $number2 );
			break;

		case '*':
		case 'mul':
		case 'multiply':
			$result = ( $bc ) ? bcmul( $number1, $number2, $precision ) /* string */ : ( $number1 * $number2 );
			break;

		case '/':
		case 'div':
		case 'divide':
			if ( $bc ) {
				$result = bcdiv( $number1, $number2, $precision ); // String, or NULL if right_operand is 0.
			}
			else if ( $number2 != 0 ) {
				$result = $number1 / $number2;
			}

			if ( ! isset( $result ) ) {
				$result = 0;
			}
			break;

		case '%':
		case 'mod':
		case 'modulus':
			if ( $bc ) {
				$result = bcmod( $number1, $number2, $precision ); // String, or NULL if modulus is 0.
			}
			else if ( $number2 != 0 ) {
				$result = $number1 % $number2;
			}

			if ( ! isset( $result ) ) {
				$result = 0;
			}
			break;

		case '=':
		case 'comp':
		case 'compare':
			$compare = true;
			if ( $bc ) {
				$result = bccomp( $number1, $number2, $precision ); // Returns int 0, 1 or -1.
			}
			else {
				$result = ( $number1 == $number2 ) ? 0 : ( ( $number1 > $number2 ) ? 1 : -1 );
			}
			break;
	}

	if ( isset( $result ) ) {
		if ( $compare === false ) {
			if ( $round === true ) {
				$result = round( floatval( $result ), $decimals );
				if ( $decimals === 0 ) {
					$result = (int) $result;
				}
			}
			else {
				$result = ( intval( $result ) == $result ) ? intval( $result ) : floatval( $result );
			}
		}
		return $result;
	}
	return false;
}