在单独的php文件中调用函数中的查询

Good day! I'm new to PHP and I'm stuck on this. The problem is, how can I load an specific function from a class into the php file. This is all I got:

HTML FILE

<form action="myfile.php" method="post">
    <input type="text" name="subject"/>
    <input type="text" name="section"/>
    <input type="submit" name="submit"/>
</form>

PHP FILE

<?php 
include 'class_lib.php';

    $subject = $_POST['subject'];
    $section = $_POST['section'];

if(isset($_POST['submit'])){
$class = new myClass;
$success = $class->insertFunction();
if($success == TRUE)
{echo 'Inserted';}
else
{echo 'Error';}
}
?>

FUNCTION FILE

class myClass{
    function insertFunction(){
     $sql = "Insert into tblName (subject, section) VALUES($subject,$section)";
     $success = mysql_query($sql) or die (mysql_error());

    return $success;
    }
}

The problem is when I submit the button it gives me a blank page. Please help me, i'm new with this so spare with me. Any help is much appreciated.

There are multiple ways to get the values available to the class-function,
lets try the quick fix -

1. Instead of - $success = $class->insertFunction();

write

$success = $class->insertFunction($subject, $section); //Pass the parameters

and

class myClass{ function insertFunction($subject, $section){ //Get the parameter values [....] } }

Now check the value of $success. If the query was successfully executed then the value should be the primary key (auto-increment). I hope the database table has such a field.

2. Now lets do it in the proper way -

Add two properties to the class file -

class myClass{

    public $subject;
    public $section;

    function insertFunction(){
        $sql = "Insert into tblName (subject, section) VALUES($this->subject, $this->section)";
        return mysql_query($sql);
    }
}

Then change the .php file as -

<?php
    include 'class_lib.php';
    [......] //include your class file.

    $subject = $_POST['subject'];
    $section = $_POST['section'];

    if(isset($_POST['submit'])) {
        $class = new myClass;
        $class->subject = $subject;
        $class->section = $section;

        $success = $class->insertFunction();
        if($success)
            echo 'Inserted';
        else
            echo 'Error';
    }
?>

I hope it gives some idea.