


Analysis of Singleton Pattern Examples of PHP Design Pattern
This article mainly introduces the Singleton Pattern of PHP Design Pattern, and analyzes the principles and related usage techniques of Singleton Pattern with examples. , has certain reference value, friends in need can refer to it
The example in this article describes the singleton mode of PHP design pattern. Share it with everyone for your reference. The specific analysis is as follows:
Singleton mode (responsibility mode):
To put it simply, an object (you need to understand object-oriented thinking before learning design patterns) is only responsible for a specific task;
Single instance class:
1. The constructor needs to be marked private (access control: prevent external code from using the new operator to create objects). Singleton classes cannot be instantiated in other classes and can only be instantiated by themselves;
2. Have a static member variable that holds an instance of the class
3. Have a public static method to access this instance (the getInstance() method is commonly used to instantiate a singleton class, and the instanceof operator can be used to detect whether the class has been instantiated)
In addition, you need to create a __clone() method to prevent the object from being copied (cloned)
Why use PHP singleton pattern?
1. PHP is mainly used in database applications, so there will be a large number of database operations in an application. Using the singleton mode can avoid a large number of resources consumed by new operations.
2. If a class is needed in the system to globally control certain configuration information, it can be easily implemented using the singleton mode. This can be found in the FrontController section of ZF.
3. In a page request, it is easy to debug because all the code (such as database operation class db) is concentrated in one class. We can set hooks in the class and output logs to avoid var_dump and echo everywhere.
Code implementation:
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/1** * Design Pattern Singleton Pattern * $_instance must be declared as a static private variable * The constructor and destructor must be declared private to prevent external programs from new * class thus loses the meaning of singleton pattern * The getInstance() method must be set to public and this method must be called * to return a reference to the instance *::Operator can only access static variables and static functions * new objects will consume memory * Usage scenarios: The most commonly used place is database connection. * After using singleton mode to generate an object, * This object can be used by many other objects. */ class Danli { //Save static member variables of class instances private static $_instance; //Construction method of private tag private function __construct(){ echo 'This is a Constructed method;'; } //Create the __clone method to prevent the object from being copied and cloned public function __clone(){ trigger_error('Clone is not allow!',E_USER_ERROR); } //Singleton method, a public static method used to access the instance public static function getInstance(){ if(!(self::$_instance instanceof self)){ self::$_instance = new self; } return self::$_instance; } public function test(){ echo 'Calling method successfully'; } } //Using new to instantiate a class with a private mark constructor will report an error //$danli = new Danli(); //The correct method is to use the double colon::operator to access the static method to obtain the instance $danli = Danli::getInstance(); $danli->test(); //Copying (cloning) the object will result in an E_USER_ERROR $danli_clone = clone $danli; |
I hope this article will be helpful to everyone’s PHP programming design.

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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