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How Can I Safely Evaluate Mathematical Formulas Passed as Strings in PHP?
How Can I Safely Evaluate Mathematical Formulas Passed as Strings in PHP?
Dec 08, 2024 pm 04:36 PM
How to evaluate formula passed as string in PHP?
Problem:
I'm trying to figure out the proper and safer way to execute mathematical operation passed as string. In my scenario it is values fetched from image EXIF data.
After little research I found two way of doing it.
function calculator1($str){
eval("$str = $str;");
return $str;
}
function calculator2($str){
$fn = create_function("", "return ({$str});" );
return $fn();
};
Both examples require string cleanup to avoid malicious code execution. Is there any other or shorter way of doing so?
Answer:
function calculator3($str){
$m = new EvalMath;
return $m->evaluate($str);
}
This method uses the EvalMath class, which is specifically designed to safely evaluate mathematical expressions from untrusted sources. It provides robust error checking and only evaluates a limited set of functions.
Here's an example of how to use it:
$str = '2+2'; $result = calculator3($str); echo $result; // Output: 4
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