Home Backend Development PHP Tutorial 高手帮小弟我看上这个代码,请帮忙注释上,多谢

高手帮小弟我看上这个代码,请帮忙注释上,多谢

Jun 13, 2016 am 10:34 AM
mysql query

高手帮我看下这个代码,请帮忙注释下,谢谢!

PHP code
<!--Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->//获取记录的总笔数     public function num_rows($results) {  //$results参数是select_query($sql)的返回结果         if(!is_bool($results)) {  //**********这个地方看不懂,为什么用is_bool()取反判断,这样有什么用?             $num = mysql_num_rows($results);               $this->write_log("获取的记录条数为".$num);               return $num;           } else {               return 0;           }       }  
Copy after login


------解决方案--------------------
鉴于下面有 $num = mysql_num_rows($results);
所以 if(!is_bool($results)) { 是错误的
不是逻辑类型,并不能说就一定是资源类型
------解决方案--------------------
mysql_query() 执行出错时返回 false(bool) 值。就是判断这个用的。
if(!is_bool($results)) { 如果非bool 值,则说明query 执行成功了,否则失败了。
------解决方案--------------------
值得注意的是参数$results
看你的函数,$results参数应该是数据库查询的结果。
这样的话,用is_bool判断查询是否为假就没有什么好奇怪的了.....
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
WWE 2K25: How To Unlock Everything In MyRise
1 months ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

MySQL: The Ease of Data Management for Beginners MySQL: The Ease of Data Management for Beginners Apr 09, 2025 am 12:07 AM

MySQL is suitable for beginners because it is simple to install, powerful and easy to manage data. 1. Simple installation and configuration, suitable for a variety of operating systems. 2. Support basic operations such as creating databases and tables, inserting, querying, updating and deleting data. 3. Provide advanced functions such as JOIN operations and subqueries. 4. Performance can be improved through indexing, query optimization and table partitioning. 5. Support backup, recovery and security measures to ensure data security and consistency.

MySQL: Simple Concepts for Easy Learning MySQL: Simple Concepts for Easy Learning Apr 10, 2025 am 09:29 AM

MySQL is an open source relational database management system. 1) Create database and tables: Use the CREATEDATABASE and CREATETABLE commands. 2) Basic operations: INSERT, UPDATE, DELETE and SELECT. 3) Advanced operations: JOIN, subquery and transaction processing. 4) Debugging skills: Check syntax, data type and permissions. 5) Optimization suggestions: Use indexes, avoid SELECT* and use transactions.

How to open phpmyadmin How to open phpmyadmin Apr 10, 2025 pm 10:51 PM

You can open phpMyAdmin through the following steps: 1. Log in to the website control panel; 2. Find and click the phpMyAdmin icon; 3. Enter MySQL credentials; 4. Click "Login".

How to create navicat premium How to create navicat premium Apr 09, 2025 am 07:09 AM

Create a database using Navicat Premium: Connect to the database server and enter the connection parameters. Right-click on the server and select Create Database. Enter the name of the new database and the specified character set and collation. Connect to the new database and create the table in the Object Browser. Right-click on the table and select Insert Data to insert the data.

MySQL and SQL: Essential Skills for Developers MySQL and SQL: Essential Skills for Developers Apr 10, 2025 am 09:30 AM

MySQL and SQL are essential skills for developers. 1.MySQL is an open source relational database management system, and SQL is the standard language used to manage and operate databases. 2.MySQL supports multiple storage engines through efficient data storage and retrieval functions, and SQL completes complex data operations through simple statements. 3. Examples of usage include basic queries and advanced queries, such as filtering and sorting by condition. 4. Common errors include syntax errors and performance issues, which can be optimized by checking SQL statements and using EXPLAIN commands. 5. Performance optimization techniques include using indexes, avoiding full table scanning, optimizing JOIN operations and improving code readability.

How to create a new connection to mysql in navicat How to create a new connection to mysql in navicat Apr 09, 2025 am 07:21 AM

You can create a new MySQL connection in Navicat by following the steps: Open the application and select New Connection (Ctrl N). Select "MySQL" as the connection type. Enter the hostname/IP address, port, username, and password. (Optional) Configure advanced options. Save the connection and enter the connection name.

How to recover data after SQL deletes rows How to recover data after SQL deletes rows Apr 09, 2025 pm 12:21 PM

Recovering deleted rows directly from the database is usually impossible unless there is a backup or transaction rollback mechanism. Key point: Transaction rollback: Execute ROLLBACK before the transaction is committed to recover data. Backup: Regular backup of the database can be used to quickly restore data. Database snapshot: You can create a read-only copy of the database and restore the data after the data is deleted accidentally. Use DELETE statement with caution: Check the conditions carefully to avoid accidentally deleting data. Use the WHERE clause: explicitly specify the data to be deleted. Use the test environment: Test before performing a DELETE operation.

How to execute sql in navicat How to execute sql in navicat Apr 08, 2025 pm 11:42 PM

Steps to perform SQL in Navicat: Connect to the database. Create a SQL Editor window. Write SQL queries or scripts. Click the Run button to execute a query or script. View the results (if the query is executed).

See all articles