[PHP] Constants in strings
Hi all,
OK. We all know that constants cannot be accessed directly via their name
in double-quoted or heredoc strings. I knew this already but a read of
the PHP manual got me thinking.
The manual states that to get the $$ value of a variable, the form
{${var}} should be used. Therefore, I wondered if something similar
would work for constants.
Attempt 1 (just to be sure):
?php
define ('XYZ','ABC');
echo {XYZ}\n;
?
Output - {XYZ}
Attempt 2:
?php
define ('XYZ','ABC');
echo {{XYZ}}\n;
?
Output - {{XYZ}}
No luck there. I did encounter one oddity though:
?php
define ('XYZ','ABC');
echo {${XYZ}}\n;
?
Output:
PHP Notice: Undefined variable: ABC in /home/wilsond/testScripts/l7.php
on line 3
Which appears to mean that PHP is able to pick up the value of the
constant and try to access a variable with that name.
Any ideas?
Cheers
Dave
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Re: [PHP] Constants in strings
On Wed, 06 Jul 2011 12:56:21 +0100, Stuart Dallas wrote:
My guess is that the preceding $ causes PHP to interpret the next token
{XYZ} as a variable or a constant, but without that preceding $ it has
no way to know you're trying to use a constant. As Curtis points out,
the only way to insert a constant into a string is through
concatenation.
-Stuart
OK. I should have made myself clearer - I was making an observation with
regards to constant parsing in strings rather than looking for advice. My
bad.
My third example showed that {${XYZ}} would echo the value of the
variable called the value of XYZ:
?php
define ('XYZ','ABC');
$ABC=huh!;
echo {${XYZ}}\n;
?
Output - huh!
We could easily re-write the 'echo' line above to be:
echo {${constant('XYZ'}}\n;
But my example shows that PHP *is* accessing the value of a constant
without any jiggery-pokery or hacks (e.g. http://www.php.net/manual/en/
language.types.string.php#91628) as it is retrieving the value of ABC
from the XYZ constant and then looking for a variable of that name.
I admit that I'm no C coder but it may be possible (note, the word may)
that a change of code within the PHP source tree will allow us to use
something like echo {{XYZ}} to access the constant value.
Cheers
Dave
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