Understanding and Application of Classes in PHP [1]
Many PHP enthusiasts feel that it is difficult to understand and master the concept of classes in PHP during the learning process. Although they know that classes exist for a reason, However, since there are few opportunities to come into contact with and use it, I will just skip it. In fact, as long as we understand the basic concepts of PHP such as variables and functions, it will not be a problem to grasp the meaning of classes. In view of the important role of classes in PHP, this article will introduce the concepts and applications of classes in PHP with specific examples.
(1)
The so-called class refers to a collection composed of variables and functions that act on the variables. Classes provide a way to describe things in the real world. By effectively using classes, we can combine multiple variables and functions that describe the same object and use them as a whole, making the written program more intuitive, more reasonable, and easier to maintain.
To give a more popular example, we can create a class named Bike to describe a bicycle in real life. First, we set the variables in this class to include $pedals, $chain, $front wheel, $rear wheel, $brakes, and $handle. Then, we create functions such as Stop(), Accelerate(), TurnLeft() and TurnRight(). In this way, we have a class that can describe all the behaviors and properties of the bicycle object. For example, we can pass the $front wheel and $rear wheel variables into the TurnLeft() function to get some kind of output.
Some people may ask the above examples, although it is interesting, but we can use conventional variables and functions to implement the same function. Why must we insist on using such a cumbersome class? Of course, if we only need to describe a bicycle in the script, there seems to be no special value in defining a class. But what if the script needs to involve multiple bikes? If we still adopt the conventional method of defining variables and functions for each bicycle, then just tracking each variable and ensuring that the correct variable is entered into the correct function is a quite complicated task. On the contrary, if you use a class approach, you can effectively reduce the number of required variables. In addition, a defined class can also be included in other files or scripts, thereby enabling code reuse.
(2)
After understanding the concept of PHP classes, let’s take a closer look at how to create and use classes in scripts.

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。

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。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。


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