Although php is an interpreted language, it still needs to be compiled. Let me introduce to you which are compiled languages and which are interpreted languages, and what are their advantages and disadvantages.
Compiled language:
1. Use a special compiler (similar to Visual Studio under Windows) to target a specific platform (operating system) A certain high-level language source code is "translated" into machine code (including machine instructions and operands) executed by the platform's hardware at one time, and packaged into an executable program (.exe) format recognized by the platform. This conversion The process is called compilation. The compiled executable program can be separated from the development environment and run independently on a specific platform. After some programs are compiled, they may also need to link other compiled object codes, that is, assemble two or more object code modules to generate the final executable program. In this way, low-level code reuse is achieved.
2. The code of compiled language is compiled once and used repeatedly. In other words, the predecessors planted trees and the descendants enjoyed the shade.
3. C, C, Objective-C, etc. are all compiled languages
Interpreted languages:
1. In the program The source program is pre-compiled into an intermediate language before running, and then the intermediate language is executed by the interpreter
2. Every time a program in an interpreted language is executed, it needs to be compiled once, so the running efficiency of interpreted language programs is generally lower, and it cannot run independently of the interpreter.
3, C#, PHP, Python, Java, etc. are all interpreted languages.
Advantages of compiled languages:
1. One of the biggest advantages of compiled languages is its execution speed. Programs written in C/C run 30%-70% faster than the same programs written in Java.
2. Compiled programs consume less memory than interpreted programs.
Disadvantages:
1. The downside - the compiler is much more difficult to write than the interpreter
2. The compiler is debugging the program Not much help at the time - How many times have you encountered a "null pointer exception" in your C code and spent hours trying to figure out where in the code the error was.
3. Executable compiled code is much larger than the same interpreted code. For example, C/C .exe files are much larger than Java .class files with the same functionality.
4. Compiled programs are platform-specific and therefore platform-dependent.
5. Compiled programs do not support implementing security in the code - for example, a compiled program can access any area of memory and do anything it wants to your PC (mostly Viruses are written using compiled languages)
6. Due to loose security and platform dependency, compiled languages are not suitable for developing Internet or Web-based applications.
Advantages of interpreted languages:
1. Excellent debugging support. It only takes a few minutes for a PHP programmer to locate and fix a "null pointer exception" because the PHP running environment not only indicates the nature of the exception, but also gives the specific line number and function call sequence where the exception occurs (the famous stack trace information). Such convenience is not provided by compiled languages.
2. Interpreters are easier to implement than compilers
3. Excellent platform independence
4. High security-this is urgently needed for Internet applications
5. The size of the intermediate language code is much smaller than the compiled executable code
Disadvantages:
1. It takes up more Memory and CPU resources. This is because, in order to run a program written in an interpreted language, the associated interpreter must first be run. Interpreters are complex, intelligent, resource-intensive programs and they take up a lot of CPU cycles and memory.
2. The running efficiency is much slower than compiled programs. The interpreter does a lot of code optimization and runtime security checks; these extra steps take up more resources and further slow down the application.
The above content is for reference only!
Recommended tutorial: PHP video tutorial
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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。

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。

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)”。

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。


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