Hi all,
I need to combine two words to form a variable and echo it's value (defined by a constant) How can I do this in PHP? Heres the scenario:
<?
// I have a defined a constant
define("ECOSETUP", 10);
// I have a post value from a form which contains a value
$name=ECO
// I do something like this to combine the two
echo $name.'SETUP';
/*this gives me ECOSETUP as the output. What do I need to do to get 10 as my output using one line of code? I need to use the two words because I want to define differnt aspects of the same item ie SETUP, DEV,MONTHLY etc ie we will have ECOSETUP, ECODEV, ECOMONTHLY etc */
?>
Any ideas? I am sure it is pretty simple.
Thanks
?>
Renegade posted this at 22:40 — 1st January 2006.
He has: 2,944 posts
Joined: Oct 2002
Not too sure if this will work but, have your tried:
<?phpdefine("ECOSETUP\", 10);
$name=ECO
echo $name . SETUP;
?>
The single quotes are parsed as litteral or something like that so putting the constant in single quotes will actually pass what's in the quotes rather than the constant itself.
Just a guess...
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dk01 posted this at 00:01 — 2nd January 2006.
He has: 517 posts
Joined: Mar 2002
http://php.benscom.com/manual/en/language.variables.variable.php#12841
Unfortunately its not possible and is the nature of constants. Add your variable to the $_GLOBALS array instead if you wish to be able to do this.
-Jim
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Greg K posted this at 06:23 — 2nd January 2006.
He has: 1,667 posts
Joined: Nov 2003
<?php
define("ECOSETUP\",10);
define(\"TMPSETUP\",20);
$name1 = \"ECO\";
$name2 = \"TMP\";
eval(\"\$val1 = \" . $name1 . \"SETUP;\");
$val2 = constant($name2 . \"SETUP\");
echo \"val1 = $val1 \n\";
echo \"val2 = $val2 \n\";
?>
Either one of those seems to work, the second method seems to use a function designed for this. I found the second method in the link that dk01 provided.
-Greg
PS. Don't forget to make sure you have checking in place to make sure it is only calling defined constants.
[This space intentionally left blank]
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dk01 posted this at 09:07 — 2nd January 2006.
He has: 517 posts
Joined: Mar 2002
Nice find!
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dk01 posted this at 09:09 — 2nd January 2006.
He has: 517 posts
Joined: Mar 2002
BTW the second is faster because it avoids using eval. Eval is notoriously bad for your code's speed. Especially if you intend on doing it many times. Instead use the constant() method.
dk01.org | heartland-design.com | tizzap.com
mizzy posted this at 16:24 — 2nd January 2006.
They have: 47 posts
Joined: Jun 2001
Thanks all...very helpful. I have actually completed the code today...thanks to you. HAPPY NEW YEAR !!
dk01 posted this at 17:32 — 2nd January 2006.
He has: 517 posts
Joined: Mar 2002
*happy new years to you too!*
JeevesBond posted this at 20:27 — 3rd January 2006.
He has: 3,711 posts
Joined: Jun 2002
I know this is off-topic, but vBulletin (the forum software we use) uses eval all the time, does constant() perform the same functionality (parse code in a variable)?
Could you substantiate that dk01? Do you know of someone who's tested the function, maybe you could provide links? Thanks.
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dk01 posted this at 23:08 — 3rd January 2006.
He has: 517 posts
Joined: Mar 2002
I stand corrected. eval() in php is not inefficient but it is a security risk. There is debate over whether it should be used at all but most programmers agree that unless you are drawing the data from a database or trusted source then you should not use it. The reason is that it can execute arbitrary code. So for example if you have register globals on then this could be dangerous. So.. for some references. You mentioned vBulletin? Here is an exploit for that project caused by the fact that it uses eval:
http://www.osvdb.org/14047
Another few articles on the subject: http://www.sitepoint.com/blogs/2005/02/27/eval-is-dead-long-live-eval/
http://www.phpwact.org/security/functions/eval_functions?DokuWiki=064b51a8941c7b29c4e07fd16ce1...
I found this interesting because I know in javascript eval will actually make your code slower. (Try having several large eval's running in js, its notably slower)
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JeevesBond posted this at 21:53 — 4th January 2006.
He has: 3,711 posts
Joined: Jun 2002
Ah, thanks for that dk01!
Luckily most of the eval stuff in vB is pulled from a database, but in that exploit it seems that a get variable is being eval'd ... Very dangerous, they're a bit silly to allow that to happen!
Haven't had to use eval in JavaScript yet, will make a note to avoid it like the plague.
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