Eval() problem in PHP - php

Question

Quite some time ago I wrote a RSS parser. It worked fine until now, when I turned my error and notice reporting on. Currently I keep getting quite a lot of notices that tell me that something is wrong in the function. I tried solving this problem on my own, but I had no success. Could You please help me with this error?
The error:
Notice: Undefined index: RSS in C:\xampp\htdocs\Dropbox\RECtus\System\sysFiles\libarys\myRSSParser.lib(103) : eval()'d code on line 1
Notice: Undefined index: LINK in C:\xampp\htdocs\Dropbox\RECtus\System\sysFiles\libarys\myRSSParser.lib(103) : eval()'d code on line 1
The script:
function parseData($parser, $data) {
if(!trim($data)) return;
$RSS = '';
$evalcode = "\$this->output";
foreach($this->tags as $tag) {
if(is_array($tag)) {
list($tagname, $indexes) = each($tag);
$evalcode .= "[\"$tagname\"]";
if(!isset(${$tagname})) ${$tagname} = '';
if(${$tagname}) $evalcode .= "[" . (${$tagname} - 1) . "]";
if($indexes) extract($indexes);
} else {
if(preg_match("/^([A-Z]+):([A-Z]+)$/", $tag, $matches)) {
$evalcode .= "[\"$matches[1]\"][\"$matches[2]\"]";
} else {
$evalcode .= "[\"$tag\"]";
}
}
}
eval("$evalcode = $evalcode . '" . addslashes($data) . "';");
}
Line 103 is the eval() line.

Answer 1

Why are you using eval() ?
It seems you're just trying to concatenate portions of string, no ?
If so, why not just... concatenate portions of strings ?
Basically, you should be able to do something like this :
$this->output = array();
$this->output['...'] = 'some string';
$this->output['...'] = array();
$this->output['...']['...'] = 'some other string';