Explode function or from other reasons? - php

Question

I have a code in php it takes a well formatted string such as 'field,operator,value' and produces a WHERE statment to MySQL database query.
if the two fields names below end with the same characters such as 'id' like 'id' and 'classid' it produces strange behavior. such as the following test.php file:
<?php
$where = $_GET['where'];
$tokens = multiexplode(array("^", "~", "(", ")"), $where);
$where= str_replace("~"," OR ",$where);
$where = str_replace("^", " AND ", $where);
foreach ($tokens as $item) {
if (!empty($item)) {
$where = str_replace($item, getOperand($item), $where);
}
}
echo 'WHERE '.$where;
function multiexplode($delimiters, $string)
{
$unifydelimters = str_replace($delimiters, $delimiters[0], $string);
$conditions = explode($delimiters[0], $unifydelimters);
return $conditions;
}
function getOperand($item)
{
$extokens = explode (",", $item);
switch (trim($extokens[1])) {
case 'eq':
return trim($extokens[0]) . " = '" . trim($extokens[2]) . "' ";
break;
case 'neq':
return trim($extokens[0]) . " != '" . trim($extokens[2]) . "' ";
break;
default:
return "";
break;
}
}
If you test it in the browser like this:
http://localhost/test/test.php?where=id,eq,1^classid,eq,1X
Where X is any number from 0 to infnity it will echo the following line:
note that both fields id and classid end with 'id'
id = '1' AND classid='1' X
But if tested with the following urls it works fine:
http://localhost/test/test.php?where=id,eq,1^classid,eq,MX where M>1 and X is any number
http://localhost/test/test.php?where=id,eq,1^class,eq,1X , X is any digit
http://localhost/test/test.php?where=id,neq,1^classid,eq,1X,, X is any digit
Any idea why this is happenning??
Thanks,