Ever wondering to calculate 2 + 2 ? Sure you have.
But what about your formula comes into a string input ?
So, how to calculate “2 + 2″ or “4 * ( 3 – 5 )” in PHP ?

We’ll have the function calculate_string($mathstring).

function calculate_string( $mathString )	{
	$mathString = trim($mathString);     // trim white spaces
	$mathString = ereg_replace ('[^0-9\+-\*\/\(\) ]', '', $mathString);    // remove any non-numbers chars; exception for math operators

	$compute = create_function("", "return (" . $mathString . ");" );
	return 0 + $compute();
}

$string = " (1 + 1) * (2 + 2)";
echo calculate_string($string);  // outputs 8  

Posted by admin in PHP/mySQL, featured on 27th Apr, 2010

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