Detailed explanation of some simple PHP database connection examples

This article will give you PHP beginners detailed example codes for PHP connection to the database. It mainly talks about the entry-level mysql connection code to the advanced encapsulated database connection class. I hope this article will be helpful to all my friends.

Two methods to connect to MySQL database :

(1) Use PHP database function connection

This method is the most commonly used method.
Four database functions are mainly used here:
mysql_connect () establishes a connection to the MySQL server.
mysql_select_db (): Select the database in the MySQL server for subsequent data query operation query processing.
mysql_query (): Send the query string to help MySQL perform related processing or execution.
mysql_fetch_row (): used to move a single row of query result result into an array variable. The index of the array is a number
Index, the first index value is 0.

(2)Connect via ODBC

PHP mainly uses four functions to connect to the MySQL database through ODBC:
Odbc_connect (): used to establish a connection with ODBC data source.
Odbc_do (): used to perform database queries after establishing a connection.
Odbc_result(): used to obtain the value of a field in the current record row.
Odbc_fetch_row (): used to save query results to an array, each array element corresponds to a record.

Let’s first look at PHP database function connection method examples

Connect to a MySQL database

Before you can access and process data in the database, you must create a connection to the database.

In PHP, this task is accomplished through the mysql_connect() function.

Grammar

mysql_connect(servername,username,password);Parameter Description
servername is optional. Specifies the server to connect to. The default is "localhost:3306".
username is optional. Specifies the username to log in with. The default value is the name of the user who owns the server process.
password is optional. Specifies the password to use for login. The default is "".

The code is as follows

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代码如下	复制代码
$con = mysql_connect("localhost","root",""); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_close($con); ?>

$con = mysql_connect("localhost","root","");

if (!$con)

代码如下	复制代码
$mysqli = new mysqli('localhost','root','','volunteer'); if (mysqli_connect_errno()){ die('Unable to connect!'). mysqli_connect_error(); } ?>

{

die('Could not connect: ' . mysql_error());

}

代码如下	复制代码
$db = new PDO('mysql:host=localhost;dbname=test', 'root', ''); try { foreach ($db->query('select * from user') as $row){ print_r($row); } $db = null; //关闭数据库 } catch (PDOException $e) { echo $e->getMessage(); } ?>

mysql_close($con); ?> Object-oriented mysqli (detailed tutorial)

The code is as follows	Copy code
$mysqli = new mysqli('localhost','root','','volunteer');<🎜> if (mysqli_connect_errno()){<🎜> die('Unable to connect!'). mysqli_connect_error();<🎜> }<🎜> ?>

pdo connection mysql (detailed tutorial)

The code is as follows	Copy code
<🎜> $db = new PDO('mysql:host=localhost;dbname=test', 'root', '');<🎜> try {<🎜> foreach ($db->query('select * from user') as $row){ print_r($row); } $db = null; //Close database } catch (PDOException $e) { echo $e->getMessage(); } ?>

Then we can also use ODBC to connect to the database

The code is as follows

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代码如下	复制代码
require_once './adodb5/adodb.inc.php'; $conn = &ADONewConnection('mysql'); $conn->connect('localhost','root','','test'); $conn->Execute("set names utf8"); $res = $conn->Execute("select * from user"); if (!$res){ echo $conn->ErrorMsg(); }else{ var_dump($res); } ?>

require_once './adodb5/adodb.inc.php';<🎜> $conn = &ADONewConnection('mysql');<🎜> $conn->connect('localhost','root','','test'); $conn->Execute("set names utf8"); $res = $conn->Execute("select * from user"); if (!$res){ echo $conn->ErrorMsg(); }else{ var_dump($res); } ?>

mysql data connection class

The code is as follows

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//------------------------------------------------ ------------------------------------------
// ※Database() Constructor, database initial parameters
// ※Select() // ※GetRows() // ※Insert() // ※Update() // ※Delete() // ※Halt() can interrupt and display the error message */
//------------------------------------------------ ------------------------------------------
define("DATABASETYPE", "1"); //Define database type: 1 is MySql; 2 is SQL Server; 3 is Oracle; 4 is Odbc
define("SERVER", "localhost"); //Host name or IP address of the database server
define("DATABASE", "dbName"); //The name of the database to be connected
define("USER", "tableName"); //Username used to connect to the database
define("PASSWORD", "paswd"); //Password used to connect to the database

class Database {
var $dbLink; var $dbLink; //Connection handle
var $result; var $result; //query handle
var $insId; var $insId; //Insert() successfully returns the value of the AUTO_INCREMENT column

var $rows; var $rows; //Return data array

var $numRows; var $numRows; //return the number of data
var $dbHost, $dbUser, $userPassword, $database;
var $dbType = DATABASETYPE;
var $msgFlag = "yes"; //yes:show the Mysql message; no: die by show "Halted."

function Database($dbHost = SERVER, $dbUser = USER, $userPassword = PASSWORD, $database = DATABASE) {
switch ($this->dbType) {
case 1:
$this->dbLink = @mysql_pconnect($dbHost, $dbUser, $userPassword); // or die("Can't Connect to Remote Host!");

@mysql_select_db($database, $this->dbLink); // or die ("Can't Connect to Remote Host!");

                 break;
case 2:
                 break;
}
        return true;
}

/* SQL:Select() returns false and has no result */

/* SQL:GetRows() 返回查询的记录总数 */

/* SQL:Insert() */

    function Insert($table, $columns, $values) {
        $sql = "insert into $table ($columns) values ($values)";
        $this->result = @mysql_query($sql, $this->dbLink);
        if ($this->result)
            $this->insId = @mysql_insert_id($this->dbLink);
        else {
            $this->Halt($sql);
            return false;
        }
        return true;
    }

/* SQL:Update() */

    function Update($table, $setings, $condition) {
        $sql = "update $table set $setings where $condition";
        $this->result = @mysql_query($sql, $this->dbLink);
        if ($this->result)
            $this->numRows = @mysql_affected_rows($this->result);
        else {
            $this->Halt($sql);
            return false;
        }
        return true;
    }

/* SQL:Delete */

    function Delete($table, $condition) {
        $sql = "delete from $table where $condition";
        $this->result = @mysql_query($sql, $this->dbLink);
        if ($this->result)
            $this->numRows = @mysql_affected_rows($this->result);
        else {
            $this->Halt($sql);
            return false;
        }
        return true;
    }

/* Halt():error message */

    function Halt($msg) {
        if ($this->msgFlag == "yes") {
            printf("Database Query Error: %s
n", $msg);
            printf("MySql Error: %s
n", mysql_error());
        }else
            echo ""; //自定一个出错提示文件
        return false;
    }
}

switch ($db->dbType) {
    case 1:
        @mysql_close();
        break;
    case 2:
        break;
}
$db = new Database();
?>

友情提示

如果出现连接mysql数据库中文乱码我们可以在连接数据库查询之前加上mysql_query("set names utf8"); 如果你是gbk就使用gbk编编码了

Related labels：

php example getting Started about database article of Simple detailed Detailed explanation connect

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