Note that in the second example, if the database "world" does not exist, the database selected does not change. You may need to add additional code to ensure that you are connected to the correct database.
mysqli::select_db
mysqli_select_db
(PHP 5)
mysqli::select_db -- mysqli_select_db — Selects the default database for database queries
Descrizione
Stile orientato agli oggetti
bool mysqli::select_db
( string
$dbname
)Stile procedurale
Selects the default database to be used when performing queries against the database connection.
Nota:
This function should only be used to change the default database for the connection. You can select the default database with 4th parameter in mysqli_connect().
Elenco dei parametri
-
link -
Solo nello stile procedurale: un identificatore restituito da mysqli_connect() o mysqli_init()
-
dbname -
The database name.
Valori restituiti
Restituisce TRUE in caso di successo, FALSE in caso di fallimento.
Esempi
Example #1 mysqli::select_db() example
Stile orientato agli oggetti
<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "test");
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
/* return name of current default database */
if ($result = $mysqli->query("SELECT DATABASE()")) {
$row = $result->fetch_row();
printf("Default database is %s.\n", $row[0]);
$result->close();
}
/* change db to world db */
$mysqli->select_db("world");
/* return name of current default database */
if ($result = $mysqli->query("SELECT DATABASE()")) {
$row = $result->fetch_row();
printf("Default database is %s.\n", $row[0]);
$result->close();
}
$mysqli->close();
?>
Stile procedurale
<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "test");
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
/* return name of current default database */
if ($result = mysqli_query($link, "SELECT DATABASE()")) {
$row = mysqli_fetch_row($result);
printf("Default database is %s.\n", $row[0]);
mysqli_free_result($result);
}
/* change db to world db */
mysqli_select_db($link, "world");
/* return name of current default database */
if ($result = mysqli_query($link, "SELECT DATABASE()")) {
$row = mysqli_fetch_row($result);
printf("Default database is %s.\n", $row[0]);
mysqli_free_result($result);
}
mysqli_close($link);
?>
I precedenti esempi visualizzeranno:
Default database is test. Default database is world.
Vedere anche:
- mysqli_connect() - Alias di mysqli::__construct
- mysqli_real_connect() - Opens a connection to a mysql server
add a note
User Contributed Notes 3 notes
hwalker1 at btopenworld dot com ¶
2 years ago
pjasiulewicz at gmail dot com ¶
5 years ago
In some situations its useful to use this function for changing databases in general. We've tested it in production environment and it seams to be faster with switching databases than creating new connections.
vortex100 at aol dot com ¶
10 months ago
If you are on a shared server and you get the following response from your script:
Fatal error: Call to undefined function: mysqli_connect()
this mean the version of PHP your web host is using does not support mysqli or mysqli is not enabled in PHP.
