PHP base notes - NO. 1

Original ID: GUIDM

I was so busy in July that I didn't have time to update, and I didn't read all the private messages sent by everyone on CSDN, so I'm very sorry everyone.

Recently learning PHP, JavaScript advanced version is temporarily suspended.After learning PHP to update the front-end content.

The PHP column is purely a study note recorder.thanks for your support.

Table of Contents

1. Basic introduction

2. PHP program

3. PHP variables

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1. Basic introduction

• PHP: (Hypertext Preprocessor), a widely used open source general server scripting language, suitable for web development and embedded in HTML.
• A programming language that does not require compilation and is directly executed by an interpreter/virtual machine
• PHP program execution flow:

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2. PHP program

• Default extension: .php
• The php file can contain: html, css, JavaScript code.

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Several tags:

1. ASP tags:

<% PHP code %>

2. Short tag:

3. Script tags:

4. Standard markup:

1. Common tags are: standard tags.
2. ASP and short tags are basically deprecated, if you want to use them, you need to open them in the configuration file

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PHP syntax:

1. ";" indicates the end of the statement.
2. {} indicates the end of a statement.
3. The closing tag of a PHP block also automatically indicates a semicolon (so there is no need to use a semicolon on the last line of a PHP block)

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Notes

• (#)//Single line comment
• /* */Multi-line comment

/**@author:*@Function:*/

Habit: All code must be commented while writing.

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The firstAn output function

The
• echo() function outputs one or more strings.

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3. PHP variables

Variable definition: Add the corresponding variable name (memory) in the system.

• Variable declaration: $variable name.

Assignment: You can assign data to a variable (this can be done at the same time as the definition).

• Variable Naming Rules

Numbers cannot be used at the beginning of
1. .
2. There must be no spaces in between.
3. Three nomenclatures:

Underline nomenclature: Link 2 English words with underscores.Such as: one_two

Small camel case: capitalize the first letter of the second word such as: newFile

CamelCase: Capitalize the first letter of all words eg: NewFile

The mixing of html and PHP needs to be under the PHP file.

With the same variable name together, the next sentence will cover the above sentence.

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Variables

If the value stored by a variable happens to be the name of another variable, then you can get the value of another variable directly by accessing a variable: add an extra $ sign before the variable.

Process:

1. Find $a, interpret the result as "b";
2. Bind the preceding $ sign to the result b;
3. The result of the analysis is bb;

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value by variable

Assign one variable to another.

1. Value transfer: copy the value saved by the variable, and save the new value to another variable (the two variables are not related).$a=$b
2. Pass by reference: Pass the memory address where the value stored by the variable is located to another variable.Two variables point to the same memory space (two variables are the same value.) $new variable=&$old variable

//Value transfer:// pass by reference

Several partitions of memory:

Stack area, code segment, data segment, heap area.