PHP mysqli query() Method

The PHP mysqli::query() / mysqli_query() function is used to perform a query on the database.

For non-DML queries (not INSERT, UPDATE or DELETE), this function is similar to calling mysqli_real_query() followed by either mysqli_use_result() or mysqli_store_result().

Note: When passing a statement longer than max_allowed_packet of the server, this function returns different error codes depending on whether MySQL Native Driver (mysqlnd) or MySQL Client Library (libmysqlclient) is being used. The behavior is as follows:

mysqlnd on Linux returns an error code of 1153. The error message means got a packet bigger than max_allowed_packet bytes.
mysqlnd on Windows returns an error code 2006. This error message means server has gone away.
libmysqlclient on all platforms returns an error code 2006. This error message means server has gone away.

Syntax

//Object-oriented style
public mysqli::query(query, result_mode)

//Procedural style
mysqli_query(mysql, query, result_mode)

Parameters

`mysql`	`Required.` For procedural style only: Specify a mysqli object returned by mysqli_connect() or mysqli_init().
`query`	`Required.` Specify the SQL query string.
`result_mode`	`Optional.` Specify the result mode. It indicates how the result will be returned from the MySQL server. It can be one of the following: MYSQLI_STORE_RESULT (default) - returns a mysqli_result object with buffered result set. MYSQLI_USE_RESULT - returns a mysqli_result object with unbuffered result set. As long as there are pending records waiting to be fetched, the connection line will be busy and all subsequent calls will return error: Commands out of sync. To avoid the error all records must be fetched from the server or the result set must be discarded by calling mysqli_free_result(). MYSQLI_ASYNC (available with mysqlnd) - the query is performed asynchronously and no result set is immediately returned. mysqli_poll() is then used to get results from such queries. Used in combination with either MYSQLI_STORE_RESULT or MYSQLI_USE_RESULT constant.

Return Value

Returns false on failure. For successful queries which produce a result set, such as SELECT, SHOW, DESCRIBE or EXPLAIN, this function will return a mysqli_result object. For other successful queries, this function will return true.

Example: Object-oriented style

The example below shows the usage of mysqli::query() method.

<?php
//establishing connection to the database
$mysqli = new mysqli("localhost", "user", "password", "database");
if ($mysqli->connect_errno) {
  echo "Failed to connect to MySQL: ". $mysqli->connect_error;
  exit();
}

//getting query result from the database
$sql = "SELECT EmpID, Name, Age FROM Employee ORDER BY Age";
$result = $mysqli->query($sql);

//closing the connection
$mysqli->close();

//getting the number of rows in the result set
$row_cnt = $result->num_rows;
printf("Result set has %d rows.\n", $row_cnt);
?>

The output of the above code will be similar to:

Result set has 58 rows.

Example: Procedural style

The example below shows the usage of mysqli_query() function.

<?php
//establishing connection to the database
$mysqli = mysqli_connect("localhost", "user", "password", "database");
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: ". mysqli_connect_error();
  exit();
}

//getting query result from the database
$sql = "SELECT EmpID, Name, Age FROM Employee ORDER BY Age";
$result = mysqli_query($mysqli, $sql);

//closing the connection
mysqli_close($mysqli);

//getting the number of rows in the result set
$row_cnt = mysqli_num_rows($result);
printf("Result set has %d rows.\n", $row_cnt);
?>

The output of the above code will be similar to:

Result set has 58 rows.

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