A component is an instance of TComponent or its child class. The base class TComponent implements the mechanism of component properties and events.
A property can be viewed as a public variable describing a specific aspect of the component, such as the background color, the font size, etc. A property is defined by the existence of a getter and/or a setter method of a component class. For example, in TControl, we have
class TControl extends TComponent {
public function getID() {
...
}
public function setID($value) {
...
}
}
This defines a property named ID. Reading the property (e.g. echo $component->ID;) is equivalent to invoking the getter method (e.g. echo $component->getID();); and writing the property (e.g. $component->ID='Button';) is equivalent to invoking the setter method (e.g. $component->setID('Button');).
A property is read-only if it only has a getter method and no setter method. Since PHP method names are case-insensitive, property names are also case-insensitive.
A control is an instance of class TControl or its subclass. A control is a component defined in addition with user interface. The base class TControl defines the parent-child relationship among controls which reflects the containment relationship among user interface elements.