Observer mode example

Observer mode. one-to-many mode: the observer is "one", and the observer is "multiple ".
Once "1" changes, "more" changes accordingly.

In the following example:
Microsoft is "observed" and two employees are "observers ".
Once Microsoft loses money or goes bankrupt (it seems like a great deal of time), every employee will be affected accordingly.

Microsoft (class)-> Company (abstract class)-> observer (Interface)
Employee (class)-> observer (Interface)

/** <Br/> * Observer interface <br/> * method to be defined: add, remove, and notify the observer <br/> */<br/> interface subject {<br/> function registerobserver ($ employee ); <br/> function removeobserver ($ employee); <br/> function policyobserver ($ Str ); <br/>}</P> <p>/** <br/> * Observer interface <br/> * method to be defined: Corresponding update action (after notification) <br/> */<br/> interface observer {<br/> function updata ($ Str ); <br/>}</P> <p>/** <br/> * the abstract class of the company belongs to the observer. <br/> * implementation method: add, remove, and notify the observer <br/> */<br/> abstract class company implements subject {<br/> protected $ _ employee_arr = array (); // array of employee objects (employee list) <br/> protected $ _ status; // company operation status </P> <p> Public Function registerobserver ($ employee) <br/>{< br/> $ this-> _ employee_arr [] = $ employee; <br/>}</P> <p> Public Function removeobserver ($ employee) <br/>{< br/> foreach ($ this-> _ employee_arr as $ k => $ V) <br/>{< br/> if ($ V ===$ employee) unset ($ this-> _ employee_arr [$ K]); <br/>}</P> <p> Public Function policyobserver ($ Str) <br/>{< br/> // based on the list, notify employees one by one <br/> foreach ($ this-> _ employee_arr as $ v) <br/>{< br/> $ V-> updata ($ Str ); <br/>}</P> <p>/** <br/> * Microsoft inherits the COMPANY Abstract class <br/> * /<br/> class Microsoft extends company {</P> <p> public function _ construct () // listed company <br/>{< br/> $ this-> _ Status = 'operation '; <br/>}</P> <p> Public Function adduser ($ employee) // New Employee <br/>{< br/> parent :: registerobserver ($ employee); <br/>}</P> <p> Public Function deluser ($ employee) // dismiss an employee <br/>{< br/> parent:: removeobserver ($ employee); <br/>}</P> <p> Public Function changestatus ($ status) // Changes in company status <br/>{< br/> switch ($ status) {<br/> case 'losses ': $ STR = 'salary demo'; break; <br/> case 'failed': $ STR = 'laid-off'; break; <br/> default: $ STR = 'normal work '; <br/>}< br/> parent: notifyobserver ($ Str ); <br/>}</P> <p>/** <br/> * implement the observer interface for employees <br/> * Implementation Method: action after receiving the notification <br/> */<br/> class employee implements observer {</P> <p> Public Function updata ($ Str) <br/>{< br/> echo $ Str. '<br/>'; // employee status <br/>}</P> <p> $ M = new Microsoft (); // Microsoft listed <br/> $ e1 = new employee (); // applicant E1 <br/> $ e2 = new employee (); // candidate E2 <br/> $ M-> adduser ($ E1); // E1 becomes a formal employee <br/> $ M-> adduser ($ E2 ); // E2 becomes a formal employee <br/> $ M-> changestatus ('login'); // The company loses money <br/>/* <br/> output at this time: <br/> pay-as-you-go <br/> */<br/> $ M-> deluser ($ E2 ); // fire employee E2 <br/> $ M-> changestatus ('failed'); // The company is closed <br/>/* <br/> output at this time: <br/> laid-off <br/> */