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Bug #10801 Variable Variables and Constants
Submitted: 2001-05-10 18:11 UTC Modified: 2001-05-10 19:26 UTC
From: mstearne at entermix dot com Assigned:
Status: Not a bug Package: Variables related
PHP Version: 4.0.4 OS: Linux 2.2
Private report: No CVE-ID: None
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From: mstearne at entermix dot com
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 [2001-05-10 18:11 UTC] mstearne at entermix dot com 
Variable variables techniques do not work when one of the
"variables" is a constant. The example below illustrates
this. This is probably the desired behavior for constants,
but was confusing for me when I was trying to figure it out.
The alternative I used was to add the variables I needed to
the $GLOBALS array instead of defining them as constants.

<?php

define("DB_X_NAME","database1");
define("DB_Y_NAME","database2");
$DB_Z_NAME="database3";


function connectTo($databaseName){
global $DB_Z_NAME;

$fullDatabaseName="DB_".$databaseName."_NAME";
return "\"".${$fullDatabaseName}."\"";

}

print "DB_X_NAME is ".connectTo("X")."
";
print "DB_Y_NAME is ".connectTo("Y")."
";
print "DB_Z_NAME is ".connectTo("Z")."
";

?>

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 [2001-05-10 18:56 UTC] cynic@php.net 
it's variable variables, not variable constants.
what bug are you reporting? I haven't noticed.
 [2001-05-10 19:13 UTC] mstearne at entermix dot com 
I'm not trying to change the constant value, but there
should be an interface for referencing constants similar to
how variables can be added.

If I have constants called:  MY_CONSTANT_1 and MY_CONSTANT_2

I should be about to form a variable that reference those
names like:

define("MY_CONST_1","database1");
define("MY_CONST_2","database2");

$prefix="MY_CONST_";

$whichConst="1";
$thisConst=$prefix.$whichConst."<BR>";
print $$thisConst;

$whichConst="2";
$thisConst=$prefix.$whichConst;
print $$thisConst;

That would output:
database1
database2
 [2001-05-10 19:19 UTC] cynic@php.net 
there _is_ such an interface:
http://php.net/manual/en/function.constant.php
 [2001-05-10 19:26 UTC] mstearne at entermix dot com 
Cool.  That's it.  Hmm, maybe you should classify this bug
as RTFM.  :-)
 
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