How to Dynamically Instantiate PHP Objects Based on Database Types?

Dynamically Instantiating PHP Objects from Database Types

In PHP, it is possible to dynamically create an object based on a string specifying a type defined in a database table. To achieve this, one can utilize the database query and PHP's dynamic object creation capabilities.

Consider a database table with the following columns and sample data:

id | type | propertyVal
----+------+-------------
1 | foo  | lorum
2 | bar  | ipsum

Suppose we have PHP data types defined as follows:

class ParentClass {...}
class Foo extends ParentClass {private $id, $propertyVal; ...}
class Bar extends ParentClass {private $id, $propertyVal; ...} 
// ...(more classes)...

To create an object of a type defined by the database's type column, we can leverage the following steps:

• Execute a query that selects a row with the desired id.
• Use mysql_fetch_object() to retrieve the data as an associative array.
• Obtain the type value from the associative array.
• Dynamically create an object of that type using the syntax: $instance = new $type;.
• Assign the remaining properties of the object from the associative array.

For example:

$result = mysqli_query($conn, "SELECT * FROM table WHERE id = 1");
$row = mysqli_fetch_assoc($result);

$type = $row['type'];
$instance = new $type;

unset($row['type']);  
foreach ($row as $property => $value) {
   $instance->$property = $value;
}

In this manner, the instance object will be dynamically created with the type specified by the type database column, and its properties will be assigned the values from the selected row.

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