PHP basic syntax summary

The best thing for those who have weak basic knowledge of PHP is to review the basics again, but when we look at the basics of PHP, we feel that it is too simple and we can’t understand it at all. I believe many students have had such an experience, so let’s Let’s take a look at this summary of basic PHP syntax!

1. Code identification PHP Tag

►Recommended format

►Short tag format ?>

※To use short tags, you need to modify PHP.ini->short_open_tag and restart apache

※Pure PHP code page, the end tag can be omitted "?>" is best deleted at the end of the file. This prevents accidentally added spaces or newlines from being output after the PHP closing tag.

2 Instruction separation character ";" Enter below.

3. Access method

php files cannot be opened directly and must be accessed through domain names or IP addresses. No Chinese characters can be included in the PHP file name or path!

4. Comments

►Single-line comments//Comment content (C++ style)

#Comment content (Unix Shell style)

►Multi-line comments

/*Comment content*/(C style)

※Do not wrap comments with comments

※Comments can temporarily disable the code

※Single-line comments only comment to the end of the line or the current PHP code block, which means after // ... ?> or # ... ?> The HTML code will be displayed, such as:

<h1>
    This is an <?php # echo &#39;simple&#39;; ?> example    
</h1>

5. Case Sensitity

►PHP variables are case sensitive; ►PHP language keywords, functions, custom classes and functions are not partitioned;

6. Blank Whitespace

refers to Characters without content, such as spaces, tabs, newline characters

The spaces between PHP statements will be ignored by the PHP engine.

7. Literals

Literals refer to data that can be written directly in the program, such as: 2018, 1.3, true, ' Hello May'

8. Identifier

Identifier is used to name variables, constants, functions and classes, the first character of the name It must be an ASCII letter (both upper and lower case), an underscore, or any one of the ASCII character sets 127 to 255. Only numbers and other above-mentioned characters can be used for the second character.

ASCII character set 0-127

9. Language keywords Keywords

can also be called reserved words, which are pre-set to implement the core functions of the language. They are not case-sensitive. The names of variables, methods, etc. cannot have the same name as them. Common ones are: echo, const, if, print, return, newIn addition, PHP

built-in functions

cannot have the same name as

custom functions

. 10. Single and double quotes

When single quotes contain variables,

variables are represented as strings Format output.

When double quotes contain variables,

variables are parsed and the value is output;

※In single quote strings, only Single quotes and backslashes will be treated specially.

Single quotes embedded in double quotes

$str = 'Jax said: "2017, thank you for having you"'

Double quotes embedded Single quotes

$str = "'When I rise, I will repay you'"; can also be single-embedded or double-embedded double

11. Escape

Some characters will be "specially treated" by the PHP parsing engine, so writing them needs to be escaped. To escape the characters, add the backslash "\". Just before the characters that need to be escaped, such as: echo "\"The upper part is the hall, the lower part is the kitchen, type the code, and detect the exception\""

Other conversions The defined characters are as follows:

Regular expression is a custom rule for querying and retrieving a specified string. Regular expressions are the basis, right? But regular expressions are not that easy to understand.

Review and consolidate the foundation:

php basic knowledge note sharing

php basic knowledge summary (necessary for novices)

php basics: custom functions Detailed explanation of usage examples

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