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lib_database.php
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lib_database.php
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<?php
/**
* Telegram Bot Sample
* ===================
* UWiClab, University of Urbino
* ===================
* Database support library. Don't change a thing here.
*/
function db_default_error_logging($connection, $message = "Database error") {
$errno = mysqli_errno($connection);
$error = mysqli_error($connection);
error_log("$message #$errno: $error");
}
/**
* Closes the existing connection to the database, if any.
*/
function db_close_connection() {
if(isset($GLOBALS['db_connection'])) {
$connection = $GLOBALS['db_connection'];
mysqli_close($connection);
}
unset($GLOBALS['db_connection']);
}
/**
* Creates or retrieves a connection to the database.
* @param bool $quick True if the connection should be returned untested.
* @return object A valid connection to the database.
*/
function db_open_connection($quick = false) {
if(isset($GLOBALS['db_connection'])) {
$connection = $GLOBALS['db_connection'];
if(!$quick) {
// Ping the connection just to be safe
// This can be removed for performance since we usually have no
// long-running scripts.
if(!mysqli_ping($connection)) {
error_log('Database connection already open but does not respond to ping');
die();
}
}
return $connection;
}
else {
// Check configuration
if(!DATABASE_USERNAME || !DATABASE_NAME) {
error_log('Please configure the database connection in file config.php');
die();
}
// Open up a new connection
$connection = mysqli_connect(DATABASE_HOST, DATABASE_USERNAME, DATABASE_PASSWORD, DATABASE_NAME);
if(!$connection) {
$errno = mysqli_connect_errno();
$error = mysqli_connect_error();
error_log("Failed to establish database connection. Error #$errno: $error");
die();
}
if(!mysqli_real_query($connection, 'SET NAMES utf8')) {
error_log("Failed to set connection character set to UTF8");
}
// Store connection for later
$GLOBALS['db_connection'] = $connection;
// Register clean up function for termination
register_shutdown_function('db_close_connection');
return $connection;
}
}
/**
* Performs an "action query" (UPDATE, INSERT, REPLACE, or similar)
* and returns the number of rows affected on success or the ID.
* @param string $sql SQL query to perform.
* @return bool | int Auto-generated ID for INSERT or UPDATE queries, if
* applicable, otherwise the number of affected rows.
* Returns false on failure.
*/
function db_perform_action($sql) {
$connection = db_open_connection();
if(!mysqli_real_query($connection, $sql)) {
db_default_error_logging($connection, "Failed to perform query ($sql)");
return false;
}
$generated_id = mysqli_insert_id($connection);
if($generated_id > 0) {
return $generated_id;
}
$affected_rows = mysqli_affected_rows($connection);
if($affected_rows < 0) {
db_default_error_logging($connection, "Failed to check for affected rows");
return false;
}
return $affected_rows;
}
/**
* Performs a "select query" which is expected to return one
* single scalar value.
* @param string $sql SQL query to perform.
* @return mixed The single scalar value returned by the query,
* null if no value was returned, or false on failure.
*/
function db_scalar_query($sql) {
$connection = db_open_connection();
if(!mysqli_real_query($connection, $sql)) {
db_default_error_logging($connection);
return false;
}
$result = mysqli_store_result($connection);
if($result === false) {
db_default_error_logging($connection, "Failed to store query results");
return false;
}
// Sanity checks
if(mysqli_field_count($connection) !== 1) {
mysqli_free_result($result);
error_log("Query ($sql) generated results with multiple fields (non-scalar)");
return false;
}
$num_rows = mysqli_num_rows($result);
if($num_rows > 1) {
mysqli_free_result($result);
error_log("Query ($sql) generated more than one row of results (non-scalar)");
return false;
}
else if($num_rows == 0) {
mysqli_free_result($result);
return null;
}
// Extract first row
$row = mysqli_fetch_row($result);
// Check for single (first) field type
// Field type values from: http://php.net/manual/en/mysqli-result.fetch-field.php#106064
$is_integer = false;
$field_info = mysqli_fetch_field($result);
if($field_info !== false) {
if(in_array($field_info->type, [ 16, 1, 1, 2, 9, 3, 8 ])) {
$is_integer = true;
}
}
mysqli_free_result($result);
//Error checking on results (just for the sake of it)
if($row == null) {
error_log("Failed to access first row of query results");
return false;
}
if(count($row) < 1) {
error_log("Results row is empty");
return false;
}
// Extract and return first field
if($is_integer) {
return intval($row[0]);
}
return $row[0];
}
/**
* Performs a "select query" and returns the complete
* result data as a matrix. This function is best suited
* for queries expected to return little data.
* @param string $sql SQL query to perform.
* @return bool | array The results table or false on failure.
*/
function db_table_query($sql) {
$connection = db_open_connection();
if(!mysqli_real_query($connection, $sql)) {
db_default_error_logging($connection);
return false;
}
$result = mysqli_store_result($connection);
if($result === false) {
db_default_error_logging($connection, "Failed to store query results");
return false;
}
$matrix = [];
while(($row = mysqli_fetch_row($result)) != null) {
$matrix[] = $row;
}
mysqli_free_result($result);
return $matrix;
}
/**
* Performs a "select query" and returns one row of data as
* an array. This function is inteded for queries expected to
* return only one single row of data (e.g., queries with a
* "LIMIT 1" SQL clause or with a "WHERE" clause you are sure
* evaluates to true for only one row of the table).
* This query will fail if more than one row of results is
* generated.
* @param string $sql SQL query to perform.
* @return mixed The results row as an array, null if
* no results where generated, or false on failure.
*/
function db_row_query($sql) {
$connection = db_open_connection();
if(!mysqli_real_query($connection, $sql)) {
db_default_error_logging($connection);
return false;
}
$result = mysqli_store_result($connection);
if($result === false) {
db_default_error_logging($connection, "Failed to store query results");
return false;
}
$num_rows = mysqli_num_rows($result);
if($num_rows > 1) {
mysqli_free_result($result);
error_log("Query ($sql) generated more than one row of results");
return false;
}
else if($num_rows == 0) {
mysqli_free_result($result);
return null;
}
$row = mysqli_fetch_row($result);
mysqli_free_result($result);
return $row;
}
/**
* Escapes a string to be used as a value inside an SQL query.
* @return string Escaped string.
*/
function db_escape($s) {
return mysqli_real_escape_string(db_open_connection(true), (string)$s);
}