public, private and protected are called access modifiers. Just like C, PHP also has three access modifiers such as public, private and protected. The visibility of a property, method or constant can be defined by preceding the declaration with these keywords.
#1. If a class member is declared public, then it can be accessed from anywhere.
2. If a class member is declared protected, it can only be accessed within the class itself and in inheritance and parent classes.
3. If a class member is declared private, it can only be accessed by the class that defines the member.
public: This modifier can be used both internally and externally.
Example:
<?php class pub { public $tag_line = "PHP中文网!"; function display() { echo $this->tag_line."<br/>"; } } class child extends pub { function show(){ echo $this->tag_line; } } $obj= new child; echo $obj->tag_line."<br/>"; $obj->display(); $obj->show();
Output:
PHP中文网! PHP中文网! PHP中文网!
protected: This modifier can be used in the class in which it is defined and its parent or inherited class .
Example:
<?php class pro { protected $x = 500; protected $y = 500; function sub() { echo $sum=$this->x-$this->y . "<br/>"; } } class child extends pro { function mul() { echo $sub=$this->x*$this->y; } } $obj= new child; $obj->sub(); $obj->mul(); ?>
Output:
0 250000
private: This modifier can be used in the class in which it is defined. (It cannot be accessed outside the class means inherited class).
Example:
<?php class demo { private $name="PHP中文网"; private function show() { echo "这是基(父)类的私有方法"; } } class child extends demo { function display() { echo $this->name; } } $obj= new child; $obj->show(); $obj->display();
Output: The error shown in the figure is because private class data cannot be accessed outside the class.
Related recommendations: "PHP Tutorial"http://www.php.cn/course/list/29.html
This article This article is an introduction to the differences between public, private and protected in PHP. I hope it will be helpful to friends in need!
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php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($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。

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。

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。

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。

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。

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。


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