PHP Keywords

PHP Keywords （PHP关键字）

Understanding PHP Keywords #

Understanding PHP Keywords （了解PHP关键词）

Keywords are predefined, reserved words used in programming languages that cannot be used as identifiers for variables, functions, classes, or other elements in a program. In this article, we will discuss the PHP keywords and their usage. （关键字是在编程语言中使用的预定义保留字，不能用作程序中的变量、函数、类或其他元素的标识符。在本文中，我们将讨论PHP关键字及其用法。）

What are PHP Keywords? #

What are PHP Keywords? （什么是PHP关键字？）

PHP keywords are predefined, reserved words in PHP that are used to perform specific functions. These keywords are reserved by PHP and cannot be used as variable names, function names, or class names. PHP keywords are case-insensitive, meaning that they can be written in either upper or lower case letters. （PHP关键字是PHP中用于执行特定功能的预定义保留字。这些关键字由PHP保留，不能用作变量名、函数名或类名。PHP关键字不区分大小写，这意味着它们可以用大写或小写字母书写。）

List of PHP Keywords #

List of PHP Keywords （PHP关键字列表）

Here is a list of PHP keywords:

abstract   and       array     as        break     callable
case       catch     class     clone     const     continue
declare    default   die       do        echo      else
elseif     empty     enddeclare endfor   endforeach endif
endswitch  endwhile  extends   final     finally   for
foreach    function  global    goto      if        implements
include    include_once   instanceof  insteadof  interface
isset      list      namespace new       or        print
private    protected public    require   require_once return
static     switch    throw     trait     try       unset
use        var       while     xor       yield     __halt_compiler

Usage of PHP Keywords #

Usage of PHP Keywords （PHP关键字的使用）

Keywords are used in PHP to define certain statements, constructs, and functions. For example, the if keyword is used to define a conditional statement, the while keyword is used to define a loop, and the function keyword is used to define a function. （关键字在PHP中用于定义某些语句、构造和函数。例如， if关键字用于定义条件语句， while关键字用于定义循环， function关键字用于定义函数。）

Here is an example of using some of the PHP keywords:

<?php

$x = 7;
// Define a conditional statement
if ($x == 5) {
   echo "x is equal to 5.";
}

// Define a loop
for ($i = 0; $i < 10; $i++) {
   echo $i;
}

// Define a function
function add($a, $b)
{
   return $a + $b;
}
?>

In this example, we use the if keyword to define a conditional statement that checks whether the value of $x is equal to 5. We use the for keyword to define a loop that iterates from 0 to 9. Finally, we use the function keyword to define a function that takes two parameters and returns their sum. （在此示例中，我们使用if关键字定义一个条件语句，用于检查$ x的值是否等于5。我们使用for关键字定义从0迭代到9的循环。最后，我们使用function关键字定义一个函数，该函数接受两个参数并返回其总和。）

Conclusion #

Conclusion （小结）

Keywords are an important part of any programming language, including PHP. By understanding the meaning and usage of PHP keywords, you can write more effective and efficient code. In addition, using keywords correctly can help prevent errors and make your code more readable and maintainable. （关键字是任何编程语言（包括PHP ）的重要组成部分。通过了解PHP关键字的含义和用法，您可以编写更有效和高效的代码。此外，正确使用关键字有助于防止错误，并使代码更具可读性和可维护性。）