The behaviour of these functions is affected by settings in php.ini.
|mysqlnd.collect_statistics||"1"||PHP_INI_SYSTEM||Available since PHP 5.3.0.|
|mysqlnd.collect_memory_statistics||"0"||PHP_INI_SYSTEM||Available since PHP 5.3.0.|
|mysqlnd.debug||"0"||PHP_INI_SYSTEM||Available since PHP 5.3.0.|
|mysqlnd.net_read_timeout||"31536000"||PHP_INI_SYSTEM||Available since PHP 5.3.0.|
|mysqlnd.net_cmd_buffer_size||5.3.0 - "2048", 5.3.1 - "4096"||PHP_INI_SYSTEM||Available since PHP 5.3.0.|
|mysqlnd.net_read_buffer_size||"32768"||PHP_INI_SYSTEM||Available since PHP 5.3.0.|
Here's a short explanation of the configuration directives.
Enables the collection of various client statistics which can be accessed through mysqli_get_client_stats(), mysqli_get_connection_stats(), mysqli_get_cache_stats() and are shown in mysqlnd section of the output of the phpinfo() function as well.
This configuration setting enables all MySQL Native Driver statistics except those relating to memory management.
Enable the collection of various memory statistics which can be accessed through mysqli_get_client_stats(), mysqli_get_connection_stats(), mysqli_get_cache_stats() and are shown in mysqlnd section of the output of the phpinfo() function as well.
This configuration setting enables the memory management statistics within the overall set of MySQL Native Driver statistics.
Records communication from all extensions using mysqlnd to the specified log file.
The format of the directive is mysqlnd.debug = "option1[,parameter_option1][:option2[,parameter_option2]]".
The options for the format string are as follows:
A[,file] - Appends trace output to specified file. Also ensures that data is written after each write. This is done by closing and reopening the trace file (this is slow). It helps ensure a complete log file should the application crash.
a[,file] - Appends trace output to the specified file.
d - Enables output from DBUG_<N> macros for the current state. May be followed by a list of keywords which selects output only for the DBUG macros with that keyword. An empty list of keywords implies output for all macros.
f[,functions] - Limits debugger actions to the specified list of functions. An empty list of functions implies that all functions are selected.
F - Marks each debugger output line with the name of the source file containing the macro causing the output.
i - Marks each debugger output line with the PID of the current process.
L - Marks each debugger output line with the name of the source file line number of the macro causing the output.
n - Marks each debugger output line with the current function nesting depth
o[,file] - Similar to a[,file] but overwrites old file, and does not append.
O[,file] - Similar to A[,file] but overwrites old file, and does not append.
t[,N] - Enables function control flow tracing. The maximum nesting depth is specified by N, and defaults to 200.
x - This option activates profiling.
This feature is only available with a debug build of PHP. Works on Microsoft Windows if using a debug build of PHP and PHP was built using Microsoft Visual C version 9 and above.
mysqlnd and the MySQL Client Library, libmysql use different networking APIs. mysqlnd uses PHP streams, whereas libmysql uses its own wrapper around the operating level network calls. PHP, by default, sets a read timeout of 60s for streams. This is set via php.ini, default_socket_timeout. This default applies to all streams that set no other timeout value. mysqlnd does not set any other value and therefore connections of long running queries can be disconnected after default_socket_timeout seconds resulting in an error message "2006 - MySQL Server has gone away". The MySQL Client Library sets a default timeout of 365 * 24 * 3600 seconds (1 year) and waits for other timeouts to occur, such as TCP/IP timeouts. mysqlnd now uses the same very long timeout. The value is configurable through a new php.ini setting: mysqlnd.net_read_timeout. mysqlnd.net_read_timeout gets used by any extension (ext/mysql, ext/mysqli, PDO_MySQL) that uses mysqlnd. mysqlnd tells PHP Streams to use mysqlnd.net_read_timeout. Please note that there may be subtle differences between MYSQL_OPT_READ_TIMEOUT from the MySQL Client Library and PHP Streams, for example MYSQL_OPT_READ_TIMEOUT is documented to work only for TCP/IP connections and, prior to MySQL 5.1.2, only for Windows. PHP streams may not have this limitation. Please check the streams documentation, if in doubt.
mysqlnd allocates an internal command/network buffer of mysqlnd.net_cmd_buffer_size (in php.ini) bytes for every connection. If a MySQL Client Server protocol command, for example, COM_QUERY ("normal" query), does not fit into the buffer, mysqlnd will grow the buffer to the size required for sending the command. Whenever the buffer gets extended for one connection, command_buffer_too_small will be incremented by one.
If mysqlnd has to grow the buffer beyond its initial size of mysqlnd.net_cmd_buffer_size bytes for almost every connection, you should consider increasing the default size to avoid re-allocations.
The default buffer size is 2048 bytes in PHP 5.3.0. In later versions the default is 4096 bytes. The default can changed either through the php.ini setting mysqlnd.net_cmd_buffer_size or using mysqli_options(MYSQLI_OPT_NET_CMD_BUFFER_SIZE, int size).
It is recommended that the buffer size be set to no less than 4096 bytes because mysqlnd also uses it when reading certain communication packet from MySQL. In PHP 5.3.0, mysqlnd will not grow the buffer if MySQL sends a packet that is larger than the current size of the buffer. As a consequence, mysqlnd is unable to decode the packet and the client application will get an error. There are only two situations when the packet can be larger than the 2048 bytes default of mysqlnd.net_cmd_buffer_size in PHP 5.3.0: the packet transports a very long error message, or the packet holds column meta data from COM_LIST_FIELD (mysql_list_fields() and the meta data come from a string column with a very long default value (>1900 bytes).
As of PHP 5.3.2 mysqlnd does not allow setting buffers smaller than 4096 bytes.
The value can also be set using mysqli_option(link, MYSQLI_OPT_NET_CMD_BUFFER_SIZE, size).
Maximum read chunk size in bytes when reading the body of a MySQL command packet. The MySQL client server protocol encapsulates all its commands in packets. The packets consist of a small header and a body with the actual payload. The size of the body is encoded in the header. mysqlnd reads the body in chunks of MIN(header.size, mysqlnd.net_read_buffer_size) bytes. If a packet body is larger than mysqlnd.net_read_buffer_size bytes, mysqlnd has to call read() multiple times.
The value can also be set using mysqli_optionS(link, MYSQLI_OPT_NET_READ_BUFFER_SIZE, size).