DB Driver Reference

This is the platform-independent base DB implementation class. This class will not be called directly. Rather, the adapter class for the specific database will extend and instantiate it.

The how-to material for this has been split over several articles. This article is intended to be a reference for them.

Important

Not all methods are supported by all database drivers, some of them may fail (and return FALSE) if the underlying driver does not support them.

class CI_DB_driver

initialize()

Returns:TRUE on success, FALSE on failure Return type:bool

Initialize database settings, establish a connection to the database.

db_connect($persistent = TRUE)

Parameters:

• $persistent (bool) – Whether to establish a persistent connection or a regular one

Returns:

Database connection resource/object or FALSE on failure

Return type:

mixed

Establish a connection with the database.

Note

The returned value depends on the underlying driver in use. For example, a mysqli instance will be returned with the ‘mysqli’ driver.

db_pconnect()

Returns:Database connection resource/object or FALSE on failure Return type:mixed

Establish a persistent connection with the database.

Note

This method is just an alias for db_connect(TRUE).

reconnect()

Returns:TRUE on success, FALSE on failure Return type:bool

Keep / reestablish the database connection if no queries have been sent for a length of time exceeding the server’s idle timeout.

db_select([$database = ''])

Parameters:

• $database (string) – Database name

Returns:

TRUE on success, FALSE on failure

Return type:

bool

Select / switch the current database.

db_set_charset($charset)

Parameters:

• $charset (string) – Character set name

Returns:

TRUE on success, FALSE on failure

Return type:

bool

Set client character set.

platform()

Returns:Platform name Return type:string

The name of the platform in use (mysql, mssql, etc…).

version()

Returns:The version of the database being used Return type:string

Database version number.

query($sql[, $binds = FALSE[, $return_object = NULL]])

Parameters:

• $sql (string) – The SQL statement to execute
• $binds (array) – An array of binding data
• $return_object (bool) – Whether to return a result object or not

Returns:

TRUE for successful “write-type” queries, CI_DB_result instance (method chaining) on “query” success, FALSE on failure

Return type:

mixed

Execute an SQL query.

Accepts an SQL string as input and returns a result object upon successful execution of a “read” type query.

Returns:

• Boolean TRUE upon successful execution of a “write type” queries
• Boolean FALSE upon failure
• CI_DB_result object for “read type” queries

simple_query($sql)

Parameters:

• $sql (string) – The SQL statement to execute

Returns:

Whatever the underlying driver’s “query” function returns

Return type:

mixed

A simplified version of the query() method, appropriate for use when you don’t need to get a result object or to just send a query to the database and not care for the result.

affected_rows()

Returns:Number of rows affected Return type:int

Returns the number of rows changed by the last executed query.

Useful for checking how much rows were created, updated or deleted during the last executed query.

trans_strict([$mode = TRUE])

Parameters:

• $mode (bool) – Strict mode flag

Return type:

void

Enable/disable transaction “strict” mode.

When strict mode is enabled, if you are running multiple groups of transactions and one group fails, all subsequent groups will be rolled back.

If strict mode is disabled, each group is treated autonomously, meaning a failure of one group will not affect any others.

trans_off()

Return type:void

Disables transactions at run-time.

trans_start([$test_mode = FALSE])

Parameters:

• $test_mode (bool) – Test mode flag

Returns:

TRUE on success, FALSE on failure

Return type:

bool

Start a transaction.

trans_complete()

Returns:TRUE on success, FALSE on failure Return type:bool

Complete Transaction.

trans_status()

Returns:TRUE if the transaction succeeded, FALSE if it failed Return type:bool

Lets you retrieve the transaction status flag to determine if it has failed.

compile_binds($sql, $binds)

Parameters:

• $sql (string) – The SQL statement
• $binds (array) – An array of binding data

Returns:

The updated SQL statement

Return type:

string

Compiles an SQL query with the bind values passed for it.

is_write_type($sql)

Parameters:

• $sql (string) – The SQL statement

Returns:

TRUE if the SQL statement is of “write type”, FALSE if not

Return type:

bool

Determines if a query is of a “write” type (such as INSERT, UPDATE, DELETE) or “read” type (i.e. SELECT).

elapsed_time([$decimals = 6])

Parameters:

• $decimals (int) – The number of decimal places

Returns:

The aggregate query elapsed time, in microseconds

Return type:

string

Calculate the aggregate query elapsed time.

total_queries()

Returns:The total number of queries executed Return type:int

Returns the total number of queries that have been executed so far.

last_query()

Returns:The last query executed Return type:string

Returns the last query that was executed.

escape($str)

Parameters:

• $str (mixed) – The value to escape, or an array of multiple ones

Returns:

The escaped value(s)

Return type:

mixed

Escapes input data based on type, including boolean and NULLs.

escape_str($str[, $like = FALSE])

Parameters:

• $str (mixed) – A string value or array of multiple ones
• $like (bool) – Whether or not the string will be used in a LIKE condition

Returns:

The escaped string(s)

Return type:

mixed

Escapes string values.

Warning

The returned strings do NOT include quotes around them.

escape_like_str($str)

Parameters:

• $str (mixed) – A string value or array of multiple ones

Returns:

The escaped string(s)

Return type:

mixed

Escape LIKE strings.

Similar to escape_str(), but will also escape the % and _ wildcard characters, so that they don’t cause false-positives in LIKE conditions.

Important

The escape_like_str() method uses ‘!’ (exclamation mark) to escape special characters for LIKE conditions. Because this method escapes partial strings that you would wrap in quotes yourself, it cannot automatically add the ESCAPE '!' condition for you, and so you’ll have to manually do that.

primary($table)

Parameters:

• $table (string) – Table name

Returns:

The primary key name, FALSE if none

Return type:

string

Retrieves the primary key of a table.

Note

If the database platform does not support primary key detection, the first column name may be assumed as the primary key.

count_all([$table = ''])

Parameters:

• $table (string) – Table name

Returns:

Row count for the specified table

Return type:

int

Returns the total number of rows in a table, or 0 if no table was provided.

list_tables([$constrain_by_prefix = FALSE])

Parameters:

• $constrain_by_prefix (bool) – TRUE to match table names by the configured dbprefix

Returns:

Array of table names or FALSE on failure

Return type:

array

Gets a list of the tables in the current database.

table_exists($table_name)

Parameters:

• $table_name (string) – The table name

Returns:

TRUE if that table exists, FALSE if not

Return type:

bool

Determine if a particular table exists.

list_fields($table)

Parameters:

• $table (string) – The table name

Returns:

Array of field names or FALSE on failure

Return type:

array

Gets a list of the field names in a table.

field_exists($field_name, $table_name)

Parameters:

• $table_name (string) – The table name
• $field_name (string) – The field name

Returns:

TRUE if that field exists in that table, FALSE if not

Return type:

bool

Determine if a particular field exists.

field_data($table)

Parameters:

• $table (string) – The table name

Returns:

Array of field data items or FALSE on failure

Return type:

array

Gets a list containing field data about a table.

escape_identifiers($item)

Parameters:

• $item (mixed) – The item or array of items to escape

Returns:

The input item(s), escaped

Return type:

mixed

Escape SQL identifiers, such as column, table and names.

insert_string($table, $data)

Parameters:

• $table (string) – The target table
• $data (array) – An associative array of key/value pairs

Returns:

The SQL INSERT statement, as a string

Return type:

string

Generate an INSERT statement string.

update_string($table, $data, $where)

Parameters:

• $table (string) – The target table
• $data (array) – An associative array of key/value pairs
• $where (mixed) – The WHERE statement conditions

Returns:

The SQL UPDATE statement, as a string

Return type:

string

Generate an UPDATE statement string.

call_function($function)

Parameters:

• $function (string) – Function name

Returns:

The function result

Return type:

string

Runs a native PHP function , using a platform agnostic wrapper.

cache_set_path([$path = ''])

Parameters:

• $path (string) – Path to the cache directory

Return type:

void

Sets the directory path to use for caching storage.

cache_on()

Returns:TRUE if caching is on, FALSE if not Return type:bool

Enable database results caching.

cache_off()

Returns:TRUE if caching is on, FALSE if not Return type:bool

Disable database results caching.

cache_delete([$segment_one = ''[, $segment_two = '']])

Parameters:

• $segment_one (string) – First URI segment
• $segment_two (string) – Second URI segment

Returns:

TRUE on success, FALSE on failure

Return type:

bool

Delete the cache files associated with a particular URI.

cache_delete_all()

Returns:TRUE on success, FALSE on failure Return type:bool

Delete all cache files.

close()

Return type:void

Close the DB Connection.

display_error([$error = ''[, $swap = ''[, $native = FALSE]]])

Parameters:

• $error (string) – The error message
• $swap (string) – Any “swap” values
• $native (bool) – Whether to localize the message

Return type:

void

Returns:

Displays the DB error screensends the application/views/errors/error_db.php template

Return type:

string

Display an error message and stop script execution.

The message is displayed using the application/views/errors/error_db.php template.

protect_identifiers($item[, $prefix_single = FALSE[, $protect_identifiers = NULL[, $field_exists = TRUE]]])

Parameters:

• $item (string) – The item to work with
• $prefix_single (bool) – Whether to apply the dbprefix even if the input item is a single identifier
• $protect_identifiers (bool) – Whether to quote identifiers
• $field_exists (bool) – Whether the supplied item contains a field name or not

Returns:

The modified item

Return type:

string

Takes a column or table name (optionally with an alias) and applies the configured dbprefix to it.

Some logic is necessary in order to deal with column names that include the path.

Consider a query like this:

SELECT * FROM hostname.database.table.column AS c FROM hostname.database.table

Or a query with aliasing:

SELECT m.member_id, m.member_name FROM members AS m

Since the column name can include up to four segments (host, DB, table, column) or also have an alias prefix, we need to do a bit of work to figure this out and insert the table prefix (if it exists) in the proper position, and escape only the correct identifiers.

This method is used extensively by the Query Builder class.