How to make a conditional statement out of a string

Question

Is this possible at all? The idea is to have the following:

if ($some_statement) { ... }

where $some_statement variable is a string, which looks like this:

$some_statement = ' $day == "Monday" && $weather == "sunny" ';

I have experimented a little with curly brackets and eval function, but could not get any to work. Thanks guys, you rock!

Where does the string come from, is it user input? Is it trusted user input? — Pekka
– Pekka, Commented Jun 20, 2012 at 20:58
many probably find it easier to write if( $day == "Monday" && $weather == "sunny" ) — Esailija
– Esailija, Commented Jun 20, 2012 at 21:00
yes, user input should not be evaluated. Unless grate care is taken. — ctrl-alt-delor
– ctrl-alt-delor, Commented Jun 20, 2012 at 21:03

David Harkness · Accepted Answer · 2012-06-20 21:00:41Z

2

You can use eval for this, but keep in mind that the statement in the string must be a complete PHP statement.

$condition = 'return $day == "Monday" || $day == "Sunday";'; if (eval($condition)) { ... }

answered Jun 20, 2012 at 21:00

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1 Comment

Thank you, I think this would not work without "return" and ";" at the end of a string!

geon · Accepted Answer · 2012-06-20 21:03:42Z

If (eval($some_statement)) {

should work.

But don't do it unless you know what you are doing, which judging by your question you don't.

Evaluating code in a string is very dangerous, and can very easily create serious security holes.