Statements can be executed with the mysqli::query(), mysqli::real_query() and mysqli::multi_query(). The mysqli::query() function is the most common, and combines the executing statement with a buffered fetch of its result set, if any, in one call. Calling mysqli::query() is identical to calling mysqli::real_query() followed by mysqli::store_result().
Example #1 Executing queries
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("example.com", "user", "password", "database");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT)");Buffered result sets
After statement execution, results can be either retrieved all at once or read row by row from the server. Client-side result set buffering allows the server to free resources associated with the statement's results as early as possible. Generally speaking, clients are slow consuming result sets. Therefore, it is recommended to use buffered result sets. mysqli::query() combines statement execution and result set buffering.
PHP applications can navigate freely through buffered results. Navigation is fast because the result sets are held in client memory. Please, keep in mind that it is often easier to scale by client than it is to scale the server.
Example #2 Navigation through buffered results
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("example.com", "user", "password", "database");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT)");
$mysqli->query("INSERT INTO test(id) VALUES (1), (2), (3)");
$result = $mysqli->query("SELECT id FROM test ORDER BY id ASC");
echo "Reverse order...\n";
for ($row_no = $result->num_rows - 1; $row_no >= 0; $row_no--) {
$result->data_seek($row_no);
$row = $result->fetch_assoc();
echo " id = " . $row['id'] . "\n";
}
echo "Result set order...\n";
foreach ($result as $row) {
echo " id = " . $row['id'] . "\n";
}Il precedente esempio visualizzerà:
Reverse order... id = 3 id = 2 id = 1 Result set order... id = 1 id = 2 id = 3
Unbuffered result sets
If client memory is a short resource and freeing server resources as early as possible to keep server load low is not needed, unbuffered results can be used. Scrolling through unbuffered results is not possible before all rows have been read.
Example #3 Navigation through unbuffered results
<?php
$mysqli->real_query("SELECT id FROM test ORDER BY id ASC");
$result = $mysqli->use_result();
echo "Result set order...\n";
foreach ($result as $row) {
echo " id = " . $row['id'] . "\n";
}Result set values data types
The mysqli::query(), mysqli::real_query()
and mysqli::multi_query() functions are used to execute
non-prepared statements. At the level of the MySQL Client Server Protocol,
the command COM_QUERY and the text protocol are used
for statement execution. With the text protocol, the MySQL server converts
all data of a result sets into strings before sending. This conversion is done
regardless of the SQL result set column data type. The mysql client libraries
receive all column values as strings. No further client-side casting is done
to convert columns back to their native types. Instead, all values are
provided as PHP strings.
Example #4 Text protocol returns strings by default
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("example.com", "user", "password", "database");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT, label CHAR(1))");
$mysqli->query("INSERT INTO test(id, label) VALUES (1, 'a')");
$result = $mysqli->query("SELECT id, label FROM test WHERE id = 1");
$row = $result->fetch_assoc();
printf("id = %s (%s)\n", $row['id'], gettype($row['id']));
printf("label = %s (%s)\n", $row['label'], gettype($row['label']));Il precedente esempio visualizzerà:
id = 1 (string) label = a (string)
It is possible to convert integer and float columns back to PHP numbers by setting the
MYSQLI_OPT_INT_AND_FLOAT_NATIVE connection option,
if using the mysqlnd library. If set, the mysqlnd library will
check the result set meta data column types and convert numeric SQL columns
to PHP numbers, if the PHP data type value range allows for it.
This way, for example, SQL INT columns are returned as integers.
Example #5 Native data types with mysqlnd and connection option
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli();
$mysqli->options(MYSQLI_OPT_INT_AND_FLOAT_NATIVE, 1);
$mysqli->real_connect("example.com", "user", "password", "database");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT, label CHAR(1))");
$mysqli->query("INSERT INTO test(id, label) VALUES (1, 'a')");
$result = $mysqli->query("SELECT id, label FROM test WHERE id = 1");
$row = $result->fetch_assoc();
printf("id = %s (%s)\n", $row['id'], gettype($row['id']));
printf("label = %s (%s)\n", $row['label'], gettype($row['label']));Il precedente esempio visualizzerà:
id = 1 (integer) label = a (string)
See also