How to validate a symfony expression language expression

Question

I'm making a system where users can enter they own expressions. I've searched all of the internet and I can't seem to find a sample of how I could validate the user entered expression before executing it.

Is there a "standard way" or "best practice" to validate user entered expressions or do I have to roll my own validation?

EDIT

I just want to allow a user to filter a table (array), so the expressions I guess wouldn't be overly complex.

so for an array with headers like array('id', 'firstName', 'lastName', 'docId', 'profit'); I'm expecting expressions like: row.id < 2 and row.profit <= 500

Answer 1

The Symfony/ExpressionLanguage package have a SyntaxError class, and throws this exception if exist error in expression.

Control error:

use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
use Symfony\Component\ExpressionLanguage\SyntaxError;

$expressionLanguage = new ExpressionLanguage();

try {
    $expressionLanguage->evaluate('1 + b.foo');
} catch (SyntaxError $e) {
    // Error
}

But, we can not control error by types:

1. Invalid syntax
2. Variable not found
3. Unexpected token
4. Function not found
5. etc...

As solution (bad idea), you can control types via text in exception.