What should you focus on learning in PHP?

1. Explanation of mvc

(1)mvc is model model, view view, controller controller; it is a model and a A programming idea is to separate the input, output, and data processing of an application and decompose the coupling.

(2)A.. View, data collection and processing, and user requests, excluding business processes, smarty implements B. model, receives data and requests, completes related data processing, returns data, 'black box' Operation, core, PHP class library implementation C. Controller, task implementation, calling various components according to the incoming data to complete the task, passing the results to the view display, and realizing the business process.

(3) Advantages of mvc: It allows developers to only focus on a certain layer, it is easy to replace the implementation of the old layer with the new one, low dependency, reusability, standardization, scalability and maintainability.

2. The implementation principle of infinite classification.

A. Three types: (1) Recursive method: The number of queries is very large and is not recommended. (2) ajax: Click on whom to check the sub-column, then click on the sub-column and then check the sub-column. Clicked several times and checked several times (3) Blood relationship: Find all relatives at once. The path of the newly added column = the path of the parent ID - the ID of the parent column.

B. Query: select id,name,pid,path,concat(path,'-',id) as bpath from shop_menu order by bpath;

3. How to design or configure Mysql to achieve efficient use

(1) Database design, good structure, allowing partial redundancy. (2) The most suitable field attributes should be NOT NULL if possible, so that there is no need to compare NULL values ​​when querying. (3) System architecture design, table hashing, massive data hashing into several tables, clustering, and query and write separation. (4) Efficient SQL to improve efficiency. (5) Use join instead of subquery. (6) Use union to replace manually created temporary tables. (7) All results are required, only necessary data is obtained from the database. (8) Use different storage engines when necessary. For example, Innodb can reduce deadlocks and HEAP can improve query speed. (9) Use transactions, foreign keys, and indexes (10) caching technology.

4. How to prevent SQL injection

(1) Filter common database operation keywords: select, insert, update, delete, and, *, etc., or pass System function: filters by addslashes (content to be filtered). (2)PHP configuration file Register_globals=off;//Registering global variables is turned off. (3) Do not omit small quotation marks (on the tab) and single quotation marks when writing SQL. (4) High database naming skills, name some important fields according to the characteristics of the program, and use common methods to encapsulate them that are not easy to guess to avoid directly exposing SQL. (6)PHP safe mode Safe_mode=on;. (7) Turn on Magic_quotes_gpc=on; automatically convert sql statements. (8) Close the error message and write it to the system log. (9) Use mysqli or pdo preprocessing.

6. For secure user login system, please pay attention to

(1) MD5 (password string) encryption. (2) The login form name is not the same as the field to avoid exposing the table fields. (3) Use table names, field names, and passwords that are difficult to guess. (4) Verify login with verification code to prevent brute force cracking. (5) Verify whether the submitted data comes from this website. (6) Use preprocessing in the database part of the post-login processing code to perform filtering to prevent SQL injection.

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