check string contents: can be used as var?

[Oliver Saunders]

is there anyway to check if a string could be used a variable name. So
return false if the first character isn't a letter or if it contains
spaces etc.

I started writing a function that would do a load of tests because I
couldn't see any easier way of doing it:

<?
function is_valid_handle($str) {
// determines if the string provided can be used as a handle
// such as a php variable or html/css class
if (strlen($str) > 255)) return false;
if (strpos($str,' ')) return false;
// incomplete, needs more tests
return true;
}
?>

but as soon as i realised i would have to use range() to check all the
characters were valid and all that i decided there must be an easier
way. Do you guys know of one or am I just going to have to write it myself?

It was about then I had a great idea maybe if you use the variable
variable syntax you can see if it will return false but unfortunately it
does this:

<?
$foo= '5very @#bad variable name';
$$foo = 'Hi!'; // doesn't cause error
echo $$foo; // outputs Hi!
echo $5very @#bad variable name; // causes an error, obviously
?>

Seems PHP will quite happily let you store data in a variable of
whatever you like. I guess that's a nice feature. So...any ideas?

[Steve]

is there anyway to check if a string could be used a variable name. So
return false if the first character isn't a letter or if it contains
spaces etc.

See <http://www.php.net/language.variables> which provides a regular
expression to validate variabe identifiers.

---
Steve

[Oli Filth]

Oliver Saunders said the following on 18/10/2005 18:21:

is there anyway to check if a string could be used a variable name. So
return false if the first character isn't a letter or if it contains
spaces etc.

Just out of curiosity, why do you want to do this?

--
Oli

[Oliver Saunders]

> Just out of curiosity, why do you want to do this?
I'm seeing if I can create my own form abstraction classes. When you do
something like this:

$surname = new osisField;
$surname->SetName('surname');

I want setname to SetName() to be able to check to see if its parameter
can be used as a valid <input name=""> and post variable.

Thinking about it you can use any key for an array can't you. So
$_POST['45##'] is a valid key but then you can't extract() that. (See
test below)

<?
$foo = array('##56' => 'data'); // valid
echo $foo['##56']; // valid
echo extract($foo); // returns 0 variables extracted
echo $bar = '##56';
echo $$bar; // unsurprisingly undefined
?>