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mysqli_connect() Function

mysqli_connect(host, username, password, dbname, port, socket);
mysqli_connect() returns an object representing the connection to the MySQL server.

Parameter	Description
host	Specifies a host name or an IP address
username	Specifies the MySQL username
password	Specifies the MySQL password
dbname	Specifies the default database to be used
port	Specifies the port number to attempt to connect to the MySQL server
socket	Specifies the socket or named pipe to be used

Eg:
<?php
$connection = mysqli_connect("localhost","root","password","db_name");
// Check connection
if (mysqli_connect_errno())
{
echo "MySQL connection failed: " . mysqli_connect_error();
exit();
}
else
{
echo "MySQL connection successful";
}
?>

mysqli_select_db() Function

mysqli_select_db(connection_variable, database_name);
It returns boolean values (TRUE on success. FALSE on failure).

Parameter	Description
connection_variable	Specifies the MySQL connection to use
database_name	Specifies the database name to be connected

Eg:
<?php
$connection = mysqli_connect("localhost","root","pwd","db_test");
mysqli_select_db($connection, "db_test"); // selects the database 'db_test'.
mysqli_close($connection); // Close the connection to the database.
?>

mysqli_query() Function

mysqli_query(connection_variable, query, result-mode);
For successful SELECT, SHOW, DESCRIBE, or EXPLAIN queries mysqli_query() will return a mysqli_result object. For other queries it will return TRUE or FALSE.

Parameter	Description
connection_variable	Specifies the MySQL connection to use
query	Specifies the SQL query string
result-mode (not necessary)	MYSQLI_STORE_RESULT (default) MYSQLI_USE_RESULT MYSQLI_ASYNC

Eg:
<?php
$connection = mysqli_connect("localhost","root","pwd","db_test");
$result = mysqli_query($connection, "SELECT * FROM test_table");// returns result object
mysqli_close($connection); // Close the connection to the database.
?>

mysqli_fetch_row() Function

mysqli_fetch_row(result);
It returns an enumerated array representing the fetched row, null if there are no more rows in the result set, or false on failure.

Parameter	Description
result	Specifies a result set

Eg:
<?php
$connection = mysqli_connect("localhost","root","pwd","db_test");
$result = mysqli_query($connection, "SELECT * FROM test_table");
while ($each_row = mysqli_fetch_row($result))
{
echo $each_row[0];
}
mysqli_close($connection); // Close the connection to the database.
?>

mysqli_fetch_array() Function

mysqli_fetch_array(result,result-type);
It returns an array representing the fetched row, null if there are no more rows in the result set, or false on failure.

Parameter	Description
result	Specifies a result set
result-type	Specifies what type of array that should be produced. Can be one of the following values: MYSQLI_ASSOC MYSQLI_NUM MYSQLI_BOTH ( default)

Eg:
<?php
$connection = mysqli_connect("localhost","root","pwd","db_test");
$result = mysqli_query($connection, "SELECT * FROM test_table");
while ($arr = mysqli_fetch_array($result))
{
echo $arr[0];
}
mysqli_close($connection); // Close the connection to the database.
?>

mysql_result() Function

mysql_result(data,row,field);
As opposed to mysql_result(), there's no mysqli_result() function available in MySQLi. Use mysqli_fetch_array() function. The mysql_result() function returns the contents of one cell from a MySQL result set on success, or false on failure.

Parameter	Description
data	Specifies which result handle to use.
row	Specifies which row number to get. Row numbers start at 0.
field	It can be the field's offset, the field's name, or tablename.fieldname. If undefined, the first field is retrieved.

mysql_list_fields() Function

mysql_list_fields (database_name,table_name [, resource link_identifier]);
mysql_list_fields lists MySQL table fields. It returns a mysql result set for success. NULL if an error occurred. The function mysql_list_fields() is deprecated in PHP 5.4.0, and removed in PHP 7.0.0.

Parameter	Description
database_name	The name of the database that is being queried.
table_name	The name of the table that is being queried.
link_identifier	The MySQL connection. If the link identifier is not specified, the last link opened by mysql_connect() is assumed.

NB: We use the following command to list table fields in MYSQLi.
SHOW COLUMNS FROM table_name FROM db_name;

mysqli_num_fields() Function

mysqli_num_fields(result);
The mysqli_num_fields() returns the number of fields in a result set.

Parameter	Description
result	Specifies a result set

Eg:
<?php
$connection = mysqli_connect("localhost","root","pwd","db_test");
$result = mysqli_query($connection, "SELECT * FROM test_table");
$columns = mysqli_num_fields($result);
echo "Total fields in the result is:".$columns;
mysqli_close($connection); // Close the connection to the database.
?>

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