PHP中几种输出函数的区别
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echo:返回值是void,可以一次输出多个值,多个值之间用逗号分隔。echo是语言结构(language construct)也就是关键字,而并不是真正的函数,因此不能作为表达式的一部分使用。使用的时候不用加括号,加上也可以。只支持基本类型,布尔型除外,echo true的时候显示1,echo false的时候啥都没有。echo不可以输出数组类型;
print:返回值是int,只可以同时输出一个字符串,一个参数,还需要圆括号,不支持逗号分隔多个显示变量的语法有返回值;当执行失败时返回flase。print的用法和C语言相似,所以会对输出内容的%做特殊解释。print能输出数组类型的数据;
print_r:不仅可以打印变量的的值,还能显示变量类型,而且也可以显示数组和对象这样复杂的变量类型。print_r() 将把数组的指针移到最后边。使用reset()可让指针回到开始处,print_r()可以把字符串和数字简单地打印出来,而数组则以括起来的键和值得列表形式显示,并以Array开头;
printf:源于C语言中的printf()。该函数输出格式化的字符串。语法:printf("参数1",参数2):参数1=按什么格式输出;参数2=输出的变量。(%s:按字符串;%d: 按整型;%b:按二进制;%x:按16进制;%X:按16进制 大写输出;%o:按八进制; %f:按浮点型)。占位符被插入%符号之后,由数字和"\$" 组成。f=format:规定字符串以及如何格式化其中的变量;如下:printf("$%01.2f",43.2); //$43.20;$表示填充的字符;0表示位数不够在不影响原值的情况下补0;1表示输出的总宽度;%f则显示为一个浮点数;
sprintf:此并不能直接输出,先赋给一个变量,然后再输出变量。如下:
<?php $num=100.001;$a=sprintf("%d",$num);echo $a; //100?>;
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var_dump:void var_dump ( mixed expression [, mixed expression [, ...]] )功能:输出变量的内容,类型或字符串的内容,类型,长度。常用来调试。如下:
<?php $a=100;var_dump($a); //int(100) $a=100.356;var_dump($a); //float(100.356)?>;
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var_export:mixed var_export ( mixed $expression [, bool $return ] )返回关于传递给该函数的变量的结构信息,它和var_dump()类似,不同的是其返回的表示是合法的PHP 代码。你可以通过将函数的第二个参数设置为TRUE,从而返回变量的值。如下:
<?php $a = array (1, 2, array ("a", "b", "c"));//没有定义TRUE的情况;var_export ($a);$b = 3.1;$v = var_export($b, TRUE);echo $v;?>
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输出:array (0 => 1,1 => 2,2 => array (0 => 'a',1 => 'b',2 => 'c',),),3.1;
总结:echo、print、printf可以打印变量内容,但不能显示数组及系统超级变量数组;print_r和var_dump不仅可以打印数组、标量变量,还可以打印对象的内容。
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What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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