PHP tutorial for beginners

PHP Introduction Guide: First explore PHP variables and basic grammar

PHP, originally called Personal Home Page, is now known as PHP: hyper -text pre -processor, which is a common server -side script language that is widely used in Web development. It is used to handle tasks such as forms, files and database access.

PHP's advantage:

Interpretation Language:
• PHP code is executed by the web server. Open source:
It is a free open source product, which can be customized in height.
• Multi -function: PHP can be used to handle various tasks such as HTML forms, managing server files, and connecting databases.
• PHP Basic Syntheum:

PHP code is written in ordinary text files, and and tags are included.

PHP files usually include HTML tags.
• <?php One page can contain multiple PHP scripts. ?>
PHP statement ends at
• .
PHP execution process:
• ;

Server recognition: The server expands the inflation of the PHP script through

file expansion.

Request processing:

When the browser requests

file, the web server calls the PHP processor.
1. PHP execution: The server executes the PHP code and replaces the output into HTML. .php
Client output:
2. The generated HTML page is sent to the client. Users can only see the output results, and they can't see the PHP code itself. .php Note: Users can only see the output results on the page, and cannot see the PHP code.
3. Use embedded in html:
4. PHP provides

   and statements to embed HTML or other PHP files into the current script. The difference between the two is:

: If the file does not exist, the PHP will issue a warning, but the script will continue to be executed.

: If the file does not exist, the PHP will stop the script execution and issue a fatal error.

Language structure: include and

are basically the same, and they are used to output data to the screen.

The statement can bring or without parentheses: include or require.

The subtle difference between the two:
• include
There is no return value, and the
• return value is 1, so it can be used in the expression. require

Because return value is 1, it can be used in expression. echo

You can accept multiple parameters (although this usage is rare), and

can only accept one parameter. echo print print Use multiple parameters: print print()

Use multiple parameters (errors):

<code class="language-php">$result = echo "Hello";  // ❌ 错误：echo没有返回值</code>

• Faster than echo. print faster because it does not return any value; echo slower because it returns 1. print

When to use

and ? echo

Features	>	>
Return value	❌ t	✅ Back 1
Multiple parameters	✅ ✅	❌ No
Speed ​​	? Fast	? More slower
Can be used for expression	❌ No	✅ ✅

print PHP variable:

特性	echo	print
返回值	❌ 无	✅ 返回1
多个参数	✅ 是	❌ 否
速度	? 更快	? 更慢
可用于表达式	❌ 否	✅ 是

All PHP variables start with .

• $ PHP variables are global and can be accessed in any PHP script on the same page.

<code class="language-php">$result = print "Hello";  // ✅ 正确：print返回值为1
echo $result;  // 输出：1</code>

• No type declaration.

<code class="language-php">echo "Hello", ", ", "World!";  // 输出：Hello, World!</code>

• Variable names distinguishment.

<code class="language-php">print "Hello", "World";  // ❌ 错误：print() 只能接受一个参数</code>

• The variable value of the uncomfortable value is
.

<code class="language-php">$name = "Esraa";</code>

• NULL The language structure sets the variable to
.

<code class="language-php">$fruit = "apple"; 
echo $fruit;  // 输出：apple</code>

• unset The language structure is used to determine whether the variable is NULL, for example:
.

<code class="language-php">$number = 10;  // 整数
$name = "Esraa";  // 字符串</code>

• isset If an unbound variable is used in the expression, NULL will be forcibly converted to the value determined by the context. If the number is specified in the context, isset($fruit) will be forced to convert to 0; if the context specifies a string,
will be forcibly converted into an empty string.

<code class="language-php">$Fruit = "apple";  // 与$fruit是不同的变量
$fruit = "banana"; // 将覆盖之前的变量</code>

• Follow -up content: NULL NULL NULL The next article will explore the functions and arrays in PHP. You will learn how to effectively define and use functions, and explore how to use arrays to manage and operate data. This will help you build a more dynamic and organized PHP application. Stay tuned!

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