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
--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
