php 连接 mysql

ow to connect to MySQL database using PHP

Before you can get content out of your MySQL database, you must know how to establish a connection to MySQL from inside a PHP script. To perform basic queries from within MySQL is very easy. This article will show you how to get up and running.

Let's get started. The first thing to do is connect to the database.The function to connect to MySQL is called mysql_connect. This function returns a resource which is a pointer to the database connection. It's also called a database handle, and we'll use it in later functions. Don't forget to replace your connection details.

 

<?php $username = "your_name"; $password = "your_password"; $hostname = "localhost";  //connection to the database $dbhandle = mysql_connect($hostname, $username, $password)   or die("Unable to connect to MySQL"); echo "Connected to MySQL<br>"; ?>

All going well, you should see "Connected to MySQL" when you run this script. If you can't connect to the server, make sure your password, username and hostname are correct.

Once you've connected, you're going to want to select a database to work with. Let's assume the database is called 'examples'. To start working in this database, you'll need the mysql_select_db() function:

 

<?php //select a database to work with $selected = mysql_select_db("examples",$dbhandle)   or die("Could not select examples"); ?>

Now that you're connected, let's try and run some queries. The function used to perform queries is named - mysql_query(). The function returns a resource that contains the results of the query, called the result set. To examine the result we're going to use the mysql_fetch_array function, which returns the results row by row. In the case of a query that doesn't return results, the resource that the function returns is simply a value true or false.

A convenient way to access all the rows is with a while loop. Let's add the code to our script:

 

<?php //execute the SQL query and return records $result = mysql_query("SELECT id, model, year FROM cars"); //fetch tha data from the database while ($row = mysql_fetch_array($result)) {    echo "ID:".$row{'id'}." Name:".$row{'model'}."    ".$row{'year'}."<br>"; } ?>

Finally, we close the connection. Although this isn't strictly speaking necessary, PHP will automatically close the connection when the script ends, you should get into the habit of closing what you open.

 

<?php //close the connection mysql_close($dbhandle); ?>

Here is a code in full:

 

<?php $username = "your_name"; $password = "your_password"; $hostname = "localhost";  //connection to the database $dbhandle = mysql_connect($hostname, $username, $password)  or die("Unable to connect to MySQL"); echo "Connected to MySQL<br>"; //select a database to work with $selected = mysql_select_db("examples",$dbhandle)   or die("Could not select examples"); //execute the SQL query and return records $result = mysql_query("SELECT id, model,year FROM cars"); //fetch tha data from the database while ($row = mysql_fetch_array($result)) {    echo "ID:".$row{'id'}." Name:".$row{'model'}."Year: ". //display the results    $row{'year'}."<br>"; } //close the connection mysql_close($dbhandle); ?>

To create 'examples' database on your MySQL server you should run the following script:

CREATE DATABASE `examples`;
USE `examples`;
CREATE TABLE `cars` (
   `id` int UNIQUE NOT NULL,
   `name` varchar(40),
   `year` varchar(50),
   PRIMARY KEY(id)
);
INSERT INTO cars VALUES(1,'Mercedes','2000');
INSERT INTO cars VALUES(2,'BMW','2004');
INSERT INTO cars VALUES(3,'Audi','2001');