Can't Read static::$table_name after looping [closed] - php

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I get the following error messages:
Warning: PDOStatement::execute(): SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1 in /home/u522148874/public_html/includes/database-objects.php on line 27
Warning: PDOStatement::execute(): SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1 in /home/u522148874/public_html/includes/database-objects.php on line 27
Sample 1
Sample 2
When using the following code:
public function __construct(){
global $MySQLDatabase;
global $news;
$this->dbh = $MySQLDatabase->open_connection();
// Convert Table Fields in to Attributes
static::$db_fields = $this->get_dbFields(static::$table_name);
foreach(static::$db_fields as $field){
$this->$field = "";
}
}
// Get Table Fields from the Database
public function get_dbFields($table_name){
$sql = 'DESCRIBE ' . $table_name ;
$query = $this->dbh->prepare($sql);
$query->execute();
$result = $query->fetchAll(PDO::FETCH_OBJ);
// Get the quantity of the Table Columns
$count = count($result);
$field = array();
// Loop through each column to get the 'Field'
// ($count - 1) -> $count is minus 1 because array count starts with zero
// Example : Table Have 8 Columns
// $count will read it as 1 - 8 while array ($result[i]) reads it as 0 - 7
for($i = 0; $i <= ($count - 1); $i++){
$field[] = $result[$i]->Field;
}
return $field;
}
Can anyone explain to me why I am having those errors above but still can get the output (Sample 1 and Sample 2) above?
Here is my Complete Code: http://pastebin.com/xypkzs30

Answer 1

The problem is in the method DatabaseObjects::instantiate. The first line says
$object = new self;
Now, self is a reference to the current class, that means the class in which the instantiate-method is implemented (DatabaseObjects) and not the class on which it is called.
So you don't create new News objects where the table_name is defined but DatabaseObjects objects which have no table_name defined.
You can resolve this by creating new instances using the "late static binding"-version:
$object = new static;
That way the method creates new News objects. You might want to also mark the DatabaseObjects class as abstract, so no accidental instantiation occurs.
Plus you might want to globally cache the get_dbFields method - otherwise you hit the DB for every instantiation of the News class (your users might fall asleep using your app).