Three classes summarize the five design patterns of PHP

Factory pattern
Single element mode
Observer mode
Command chain mode
Strategy Mode

class people {
 private $name = '';
 private $user = null;

 private function __contract($name){/*The private definition here assists in the implementation of single element mode*/
 $this-> ;name = $name;
 }

 public static function instance($name){/*This method implements factory mode*/
 static $object = null;/*This variable implements single element mode*/
 if (is_null( $object))
 $object = new people($name);
 return $object;
 }

 public function work_in($who=null)
 {
 if (is_null($who)) echo 'error';
 else {
 $this->user[] = $who;/*This array variable implements the observer pattern*/
 echo $who->work();/*This method call implements the strategy pattern*/
 }
 }

 public function on_action($which=''){
 if (empty($which)) echo 'error';
 else {
 foreach ($this->user as $user)
 $user-> action($which);/*This method calls to implement the command chain mode*/
 }
 }
}

$people = people::instance('jack');
$people->work_in(new student);
$people->work_in(new teacher);
$people->on_action('eat');

class student {
 function work(){
 echo 'I am a student, heading towards Nine to five. ';
 }

 function action($which){
 if (method_exists($this, $which)) return $this->$which();
 else echo 'you are wrong!';
 }

 function eat(){
 echo 'I am a student and can only eat set meals. ';
 }
}

class teacher {
 function work(){
 echo 'I am a teacher, and I am busiest in the evening preparing lessons. ';
 }

 function action($which){
 if (method_exists($this, $which)) return $this->$which();
 else echo 'i can not do it!';
 }

 function eat(){
 echo 'I am a teacher and can eat big meals every day. ';
 }
}