Re: Variable within a Variable

At 06:54 PM 4/9/2006, bob pilly wrote:

Im trying to store a document template in mysql that has php var names within it and then find it in the datebase and print it out with the var names replaced with the var values.

At 04:05 PM 4/7/2006, Paul Novitski wrote:

At 02:41 PM 4/7/2006, David Clough wrote:

I have to parse the string 'Hello $foo' as it comes from the database: I don't get to construct it. I did hold out more hope for the eval function, but it seems to me that this is for PHP code in a database, not to evaluate variables.

David, please try the eval() route: it will do what you want. You say, "this is for PHP code in a database, not to evaluate variables," but evaluating variables is absolutely part of PHP code processing! Eval() will operate on "$x = 4;" just as easily as on "Hello $foo." You should not use eval() frivolously because it presents a potential vulnerability in your code. You may wish to ensure that the database text it operates on is first cleansed of any other PHP syntax -- similarly to the way we should all ensure that any incoming data is clean before we process it and incorporate it into our scripts. Here's an example of variaible evaluation: _______________________ $bar = "cat"; $foo = "Hello \$bar."; echo $foo; RESULT: Hello $bar. By escaping the $, I have made it a literal character in the text, the same as if I'd read "Hello $bar" from a database. _______________________ eval("echo \"$foo\";"); RESULT: Hello cat. This is equivalent to scripting:

        echo "$foo";
I'm using eval() to execute the echo command and interpret the PHP variable $foo.

_______________________ eval("\$dog = \$bar;"); echo "dog = " . $dog; RESULT: dog = cat Here I'm using eval() to set one PHP variable equal to another. _______________________ You can't simply write:

        eval("\$bar;");

or

        $x = eval($foo);

because everything inside the eval() parentheses needs to be a complete PHP statement. The eval() function itself doesn't return the value of an evaluated expression. To capture the value of an expression, you must evaluate a complete statement that sets a variable equal to the expression as above. _______________________ Clear as mud? Regards, Paul