Multiple methods and example codes for connecting php to mysql

mysql_connect("localhost", "root","1981427") //Connect to the server located on localhost, the user name is root
?>

Connect again Select database

@mysql_select_db("test") //Select database mydb
?>

This way you can connect to the database

Running the code appears: call to undefined function 'mysql_connect()'… failed This prompt function undefined means that there is no mysql_connect() function,

Solution: Copy the php_mysql.dll and libmysql.dll files to c:winntsystem32 (I missed libmysql.dll) Find ;extension=php_mysql in php.ini and remove the ";" in front of it Restart the server Example 1, conn.php file code:

$conn = @mysql_connect("localhost", "root", "root") or die("Database link error");
mysql_select_db("data", $conn); //data is the database name
mysql_query("set names 'gbk'"); //Use gbk Chinese encoding;
?>

index.php file code:

 include("conn.php");//Introduce the conn.php file
 $sql="select * from `table` order by id desc";
 $query=mysql_query( $sql);
 while($row=mysql_fetch_array($query)){
?>

Display data content:

=$row[user]?>

 }
?>

php to connect mysql database

Method 1: Ordinary method (process-oriented)

First, database user information:

//Generate a connection
$db_connect=mysql_connect($dbhost,$username,$userpass) or die("unable to connect to the mysql!");

//Select A database that needs to be operated
mysql_select_db($dbdatabase,$db_connect);

//Execute mysql statement
$result=mysql_query("select id,name from user");
// Extract data
 $row=mysql_fetch_row($result);

Added: ①Use @ (error control operator) before mysql_connect(), mysql_select_db() and other functions to ignore the error message generated by the system, and then we use die() to customize the error message;

②When extracting data, in addition to the mysql_fetch_row above, the common ones are mysql_fetch_assoc and mysql_fetch_array. Please refer to the php manual for specific differences;

③For the return value of the mysql_query() function, if the executed statement has a return value (such as select, show, describe, etc.), the corresponding data (on success) or false (on failure) will be returned; if the executed statement has no return value (such as delete, drop, insert, update, etc.), it returns true (when successful) or false (when failed).

Method 2: PHP object-oriented method to connect to mysql database

In fact, this method is very similar to the ordinary method. It just replaces the corresponding function with an object-oriented method and looks at the code directly.

$db=new mysqli($dbhost,$username,$userpass,$dbdatabase);
if(mysqli_connect_error()){
echo 'could not connect to database.';
exit;
}

$result=$db->query("select id,name from user");
$row=$result->fetch_row();

Mysqli is used here, which means an extension of mysql. It can interact with the database in either a process-oriented way or an object-oriented way. The only difference is that the way to call functions (object methods) is different.

Method 3: php pdo method to connect to mysql database

pdo is actually the abbreviation of php database objects, which is php database object in Chinese. It provides a unified method for PHP to interact with the database.

This is currently a popular method of connecting to a database. Its advantage is that as long as the data source is provided correctly, the rest of the basic operations on the database are the same. In other words, the same piece of code can interact with mysql, sqlite3, and of course postgresql, provided you provide the correct data source. Code to connect to mysql:

$dsn='mysql:host='.$dbhost.';dbname='.$dbdatabase.';'
$dbh=new pdo($dsn,$username,$ userpass);
sqlite3:
$dsn='sqlite3:"c:sqliteuser.db"';
$dbh=new pdo($dsn);
postgresql:
$dsn='pgsql:host='.$dbhost.' port=5432 dbname='.$dbdatabase.' user='.$username.' password='.$userpass;
$dbh=new pdo($dsn);

After successfully establishing a connection with the database, you only need to obtain data from the database or insert and update data.

sql code:

$stmt=$dbh->query('select id,name from user');
$row=$stmt->fetch();