Question

For a school project, I am creating an imaginary online banking site that acessess a database at school for imaginary account information. Every time I view account I get two mysqli errors. one on line 26 in person.class.php and another on line 52 on veiwaccounts.php I traced the main cause of that error in my person class but can’t seem to fix it in any way. The errors are

Warning: mysqli_query() expects parameter 1 to be mysqli, null given in …/person.class.php on line 26
Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, null given in …/viewaccounts.php on line 52

Here is a sample of some code from the viewaccounts.php file:

if($currentMember)
{
    $currentMember = new Person($memberid);
    $accounts =  $currentMember->retrieve_all_accounts();

    //HERE IS WHERE THE PROBLEM IS $accounts = $currentMember->retrieve_all_accounts(); 

    //Loop through accounts
    while($account = mysqli_fetch_assoc($accounts)) {
        //Retrieve balance
        $bankaccount = new Bankaccount($account['BankAccountID']);
        $bankaccount->connection = $conn;
        $balance = mysqli_fetch_assoc($bankaccount->retrieve_current_balance());

Here is the code for the person class file:

public function retrieve_all_accounts() {
    $accounts_query = "SELECT BankAccountID FROM BankAccount WHERE UserID = " .$this->memberid;
    $result = mysqli_query($this->connection, $accounts_query);
    return $result;
}

Answer 1

Change

    //Accounts
    $currentMember->connection = $conn;

    //instantiating class here since suggested code from video fails to do it.


if($currentMember)
{
    $currentMember = new Person($memberid);
    $accounts =  $currentMember->retrieve_all_accounts();

}else
{
    echo "<p>not working</p>";
}

To

if(!$currentMember) {
  $currentMember = new Person($memberid);
}
$currentMember->connection = $conn;
$accounts =  $currentMember->retrieve_all_accounts();

I would also shift this into the first PHP code block for readability.

You are instantiating a new Person only if $currentMember evaluates to TRUE – if the unserialize() call fails $currentMember will evaluate to FALSE, and that is when you should create a new object.

Also you assigned the connection property first, which will be destroyed when you create the new Person, which you are presumably doing every time otherwise you would see more warnings.

You should also refactor the entire logic that tests whether the Person was saved in the $_SESSION – for a start, sessions will serialize objects themselves so you should not need to call serialize()/unserialize(). What you should do instead is define an __autoload() function and just store the object instance in $_SESSION.

I also note that your development server seems to have short_open_tag on – turn it off, it is bad practice to use it as it is disabled pretty much everywhere in the real world.