PHP programmer interview questions and answers (simple type)

function strrev($str)
{
$len=strlen($str);
$newstr = ' ';
for($i=$len;$i> =0;$i--)
{
$newstr .= $str{$i};
}
return $newstr;
}

7. Database related (1). In terms of database design, this is the responsibility of the DBA and Architect. Design a well-structured database. When necessary, denormalize it (English is this: denormalize, I don’t know the Chinese translation) and allow partial data redundancy. , avoid JOIN operations to improve query efficiency

(2). In terms of system architecture design, table hashing is used to hash massive data into several different tables. Fast and slow tables, the fast table only retains the latest data, and the slow table is a historical archive. Cluster, main server Read & write , read only from the server, or N servers, each machine is the Master of each other (3). (1) and (2) exceed the requirements of PHP Programmer. It will be better. It doesn’t matter. Check whether there are less indexes. (4). Write efficient SQL statements and see if there are any inefficient SQL statements, such as full joins that generate Cartesian products, a large number of Group By and order by, no limit, etc. When necessary, change the database The logic is encapsulated into the stored procedure on the DBMS side. Query results are cached and each SQL statement is explained. (5). Everything you get is required. Only get the necessary data from the database. For example, to query the number of comments on an article, select count(*) ... where article_id = ? That's it. Don't select * ... where article_id first. = ?then msql_num_rows. Only send necessary SQL statements. For example, when modifying an article, if the user only modifies the title, then update... set title = ? where article_id = ? Do not set content = ? (large text) (6). Use different storage engines when necessary. For example, InnoDB can reduce deadlocks. HEAP can increase query speed by an order of magnitude.

8. Just like every programming language will have examples that answer Hello World, the textbooks of this database will all talk about the example of A transferring 50 US dollars to B's account. Just answer this. But as far as I know, enterprises that use MySQL , MySQL is rarely used to implement transaction processing. What’s more, Oracle has acquired the InnoDB company.

9. See the answer to question 7. Once that is done, the problem will be solved.

10. There is a function circulating on the Internet that uses regular expressions to match Chinese characters and then intercept them. In fact, there is a very simple solution: mb_substr(). Programmer's Home provides relevant solutions, please refer to: How to solve the garbled Chinese character string intercepted by php php string interception (application and extension of substr) Two functions for php to intercept Chinese strings (iconv_substr and mb_substr) php string interception function (can automatically clear web page tags) php function to intercept Chinese characters (utf-8 format) PHP Chinese string interception function supports multiple encodings Four php Chinese string interception functions php Chinese string interception php code to intercept Chinese string php Chinese string interception php function to intercept Chinese string php Chinese string interception (mb_substr) example PHP functions to calculate the length of Chinese strings and intercept Chinese strings Solve the problem of garbled characters when PHP intercepts UTF-8 Chinese strings Function to intercept Chinese characters-csubstr PHP Chinese string interception function