PHP design mode

1. Single-case mode

1<?PHP2 class Mysql{3     Private Static $instance=NULL;4     Private $conn;5     //construction method, set to private, does not allow the object to be obtained through new6     Private function__construct () {7         $conn=mysql_connect("localhost", "root", "" ");8     }9      Public Static functiongetinstance () {Ten         if(!self::$instanceinstanceof Self) { OneSelf::$instance=NewSelf ; A         } -         returnSelf::$instance; -     } the     //prevent users from replicating object instances -     Private function__clone () {} - } - $db=Mysql::getinstance (); +?>

2. Factory mode

1<?PHP2 //define an abstract class that allows subclasses to inherit and implement it.3 Abstract classoperation{4     Abstract  Public functionGetValue ($num 1,$num 2);//subclasses must implement this method5 }6 7 //Addition Class8 classOperationaddextendsoperation{9      Public functionGetValue ($num 1,$num 2){Ten         return $num 1+$num 2; One     } A } - //Subtraction Class - classOperationsubextendsoperation{ the      Public functionGetValue ($num 1,$num 2){ -         return $num 1-$num 2; -     } - } + //Multiplication Class - classOperationmulextendsoperation{ +      Public functionGetValue ($num 1,$num 2){ A         return $num 1*$num 2; at     } - } - //Division class - classOperationdivextendsoperation{ -      Public functionGetValue ($num 1,$num 2){ -         Try{ in             if($num 2= = 0){ -                 Throw New Exception("Divisor cannot be 0"); to}Else{ +                 return $num 1/$num 2; -             } the}Catch(Exception $e){ *             Echo"Error message:".$e-getMessage (); $         }Panax Notoginseng     } - } the /** + * Factory class, used primarily to create objects A * Function: According to the input operation symbol, the factory can instantiate the suitable object the  */ + classfactory{ -      Public Static functionCreateobj ($operate){ $         Switch($operate){ $              Case' + ': -                 return NewOperationadd (); -                  Break; the              Case‘-‘: -                 return Newoperationsub ();Wuyi                  Break; the              Case‘*‘: -                 return NewOperationmul (); Wu                  Break; -              Case‘/‘: About                 return NewOperationdiv (); $                  Break; -         } -     } - } A $test=factory::createobj ('/'); + $result=$test->getvalue (23,0); the Echo $result; -?>

PHP design mode