Why does php show undefined variable? I researched and found out that if the variables aren't set then they will likely show undefined variable. However, I used the isset function to check if the variable is undefined and if it is then set it to $varaible ="" . That didn't work and then later i tried $variable = NULL. What should I do Can you please see the code and tell me what shall i do. Thanks a million
<?php require_once("includes/connection.php")?>
<?php require_once("includes/function.php") ?>
<?php require_once("includes/header.php") ?>
<?php
if(isset($_GET['subj'])){
$sel_subj = NULL;
$sel_subj = $_GET['subj'];
} elseif (isset($_GET['page'])){
$sel_page = NULL;
$sel_page = $_GET['page'] ;
} else {
$sel_subj= NULL;
$sel_page =NULL;
}
?>
<table id = "structure" >
<tr>
<td id = "navigation" >
<ul class= "subjects" >
<?php
$subject_set = get_all_subjects();
while ($subject = mysql_fetch_array($subject_set)){ // <a href = "content.php?subj=1" >
if ($sel_subj == $subject["id"]){
echo "<li class = \"selected\" ";
}else{
echo "<li> ";
}
"<a href = \"content.php?subj=" . urlencode($subject["id"]) . "\">" . $subject["menu_name"]. "</a></li>" ;
$page_set = get_pages_for_subjects( $subject["id"] ) ;
echo " <ul class = \"pages\"> ";
while ($page = mysql_fetch_array($page_set)){
echo "<li><a href = \"content.php?page=" . urlencode($page["id"]) . "\">" . $page["menu_name"] . "</a></li>" ;
}
echo "</ul>" ;
}
?>
</ul>
</td>
<td id= "page" >
<h1> Main Area To Get Your Information </h1>
<?php echo $sel_subj ; ?> <br/>
<?php echo $sel_page ; ?> <br/>
</td>
</tr>
</table>
<?php include ("includes/footer.php") ?>
The variable im refering to is $sel_subj and $sel_page at the top of the code. Here is an attachment of the error