


PHP and PDO: How to get the total number of rows of query results
When developing web applications, we often need to retrieve data from the database and know the total number of rows of query results. By using the powerful database abstraction layer of PHP and PDO (PHP Data Objects), we can easily implement this function. This article will show you how to use PDO to get the total number of rows of a query result.
First, we need to establish a connection to the database. The following code snippet shows how to use PDO to connect to a MySQL database:
<?php $dsn = 'mysql:host=localhost;dbname=test'; $username = 'root'; $password = ''; try { $pdo = new PDO($dsn, $username, $password); echo "成功连接到数据库"; } catch (PDOException $e) { echo "数据库连接失败: " . $e->getMessage(); } ?>
Once we have established a connection to the database, we can then write a SQL query and execute it. The following code snippet shows how to use PDO to execute a query statement:
<?php $sql = "SELECT * FROM users"; $stmt = $pdo->query($sql); if ($stmt) { echo "查询成功"; } else { echo "查询失败"; } ?>
Now, we have obtained a set of query results. Next, we need to calculate the total number of rows in the query results. To achieve this, we can use PDO's rowCount() method. The following code snippet shows how to get the total number of rows in the query result:
<?php $sql = "SELECT * FROM users"; $stmt = $pdo->query($sql); if ($stmt) { $totalRows = $stmt->rowCount(); echo "查询结果的总行数为:" . $totalRows; } else { echo "查询失败"; } ?>
In this example, we first executed the query statement and stored the result in the $stmt variable. Then, use the rowCount() method of the $stmt object to get the total number of rows in the query results and store it in the $totalRows variable. Finally, we print out the total number of rows.
It should be noted that the rowCount() method is only valid for SELECT statement execution. For INSERT, UPDATE, and DELETE statements, the rowCount() method will return the number of affected rows rather than the total number of rows in the query result.
To summarize, by using PHP and PDO, we can easily get the total number of rows of the query results. Simply use PDO's rowCount() method to achieve this functionality. Hope this article helps you!
The above is the detailed content of PHP and PDO: How to get the total number of rows in query results. For more information, please follow other related articles on the PHP Chinese website!

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

查找方法:1、用strpos(),语法“strpos("字符串值","查找子串")+1”;2、用stripos(),语法“strpos("字符串值","查找子串")+1”。因为字符串是从0开始计数的,因此两个函数获取的位置需要进行加1处理。


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

Notepad++7.3.1
Easy-to-use and free code editor

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.