Undefined index error in php & mysql

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PHP

MySQL

I am working on a project, using PHP and MySQL. I have a problem that is undefined index error, i tried my best to remove it by many techniques but nothing happened, so i came here to get the correct answer i hope anyone will get me the correct reply thanks in advance.

i am using two forms in one page that is some thing like this
please check the whole code lines for forms input tag (51 to 55) and (69 to 74)

the source code is:
if($query_run = mysql_query($query)){
while($query_array = mysql_fetch_assoc($query_run)){
$TeacherFirstName = $query_array['Tfirst_name'];
$TeacherLastName = $query_array['Tlast_name'];

$fullName = $TeacherFirstName.' '.$TeacherLastName;



echo '

Teacher Name

';
echo '

'; echo '<input type="text" name="TeacherName" value="' .htmlspecialchars($fullName). '" disabled="disabled" />'; echo '<input type="submit" value="Fill Teachers Form" />

';
}
}else{
echo 'Query Failed to be executed.....';
}
echo '</form>';
?>

if($query_run = mysql_query($query)){
		while($query_array = mysql_fetch_assoc($query_run)){
		$courseTitle = $query_array['CourseTitle'];
		$courseCode = $query_array['CourseCode'];
		?>	
        <form action="course-evaluation-form.php" method="post">        			
		<tr><td>Course Title</td><td><input type="text" size="25" name="CourseTitle" disabled="disabled" value="<?=$courseTitle;?>" >
         <input type="submit" value="Fill Course Form"  />
        </td><td>Course Code</td><td>
		<?php echo $courseCode; ?></td></tr>       
        </form>

?>
and the other two files code is simple short like this
include('core/init.php');
include('include/header.php');

$coursTitle = $_POST['courseTitle'];
echo $coursTitle;
?>
Please reply me must its urgent

What I have tried:

I have tried to solve the problem which is on line numbers (51 to 55) and (69 to 74)
by many techniques which were introduced on different forums, but i couldn't find what i need