How Can I Safely Evaluate String Arithmetic Expressions in PHP?

Alternate Methods for Evaluating String Arithmetic Expressions

Despite PHP lacking a built-in function for evaluating arithmetic expressions from strings, there are alternative solutions that eliminate the need for manually separating operators and operands.

infix to postfix(RPN) parser and RPN Solver

The EOS class provides an infix parser to convert an expression like "2-1" to postfix notation (RPN), which is then evaluated by the RPN solver. The following code demonstrates:

require_once "eos.class.php";
$eq = new eqEOS();
$result = $eq->solveIF("2-1");
echo $result; // Prints 1

Other Options

• Wolfram|Alpha API: An API that can evaluate mathematical expressions.
• Sage: An open-source mathematical software system.
• Simple Parser: A basic PHP parser for evaluating simple expressions.
• phpdicecalc: A PHP library for performing dice rolls and mathematical operations.

Recommendation

While eval remains an option for expression evaluation, it's strongly discouraged due to security risks. The EOS class or other alternatives offer secure and efficient methods for solving arithmetic expressions in PHP.

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