php mysql_connect and mysql_pconnect implementation and detailed description_PHP tutorial

There are two ways to connect to the mysql database in php, such as mysql_connect and mysql_pconnect. One is a soft connection and the other is a continuous connection. The difference between the two is that one automatically closes the opened MySQL connection page when the page is browsed. If mysql_pconnect is not closed, Always connected.

There are two types of database tutorials for connecting to mysql in php tutorials, such as mysql_connect and mysql_pconnect. One is a soft connection and the other is a continuous connection. The difference between the two is that one automatically closes the opened mysql connection page when the page is browsed. If mysql_pconnect Stay connected until closed.
*/

$hostname="localhost";   //Define the mysql server name to connect to
$username="root"; //Define the username used to connect
$password=""; //Define the password used to connect
$link=mysql_connect($hostname,$username,$password); //Connect to the local mysql server
if($link) //If the connection is successful
{
echo "Successfully connected"; //Output content
}
else                  //If the connection fails
{
echo "Connection failed"; //Output content
}
//mysql_close($link) //Close the opened mysql connection

//mysql_pconnect connects to mysql database

$link=mysql_pconnect($hostname,$username,$password); //Open a persistent connection
if(!$link)                                                                                                                                               //If the connection cannot be made
{
die('Cannot connect'.mysql_error()); //Output information
exit(); //End all php operations
}
echo 'Continuous connection successful';

/*
Let’s look at the soft connection query database content

*/

$link=mysql_connect($hostname,$username,$password)or die("could not connect:".mysql_error());
//Convert encoding to support Chinese
mysql_query('set names gb2312;');
//Select operation library test
mysql_select_db("test")or die("could not select database:".mysql_error());
//Execute sql query and select name from table
$query="select name from friends";
$result=mysql_query($query)or die("query failed:".mysql_error());
//Match the result set to row loop output content
for($i=mysql_num_rows($result)-1;$i>=0;$i--)
{
//Move the pointer of the internal result, if there is no result, enter the content
if(!mysql_data_seek($result,$i))
{
echo "cannot seek to row $i:".mysql_error()."n";
Continue;
}
//Get a row from the query result as an object
if(!($row=mysql_fetch_object($result)))
continue;
//Output result content
echo "$row->name
n";
}
//Release the result set
mysql_free_result($result);

/*
Other operations

$escaped_item=mysql_escape_string($str); //Escape the string
printf("escaped string:%sn",$escaped_item); //Output the escaped result

$mydb=mysql_list_dbs($link); //List database
while($result=mysql_fetch_object($mydb)) //Traverse the result set through a loop and assign it to the object
{
echo $result->database."n"; //Output object content
echo "
";
}