db2_prepare() creates a prepared SQL statement which can
include 0 or more parameter markers (? characters)
representing parameters for input, output, or input/output. You can pass
parameters to the prepared statement using
db2_bind_param(), or for input values only, as an array
passed to db2_execute().
There are three main advantages to using prepared statements in your
Performance: when you prepare a statement, the
database server creates an optimized access plan for retrieving data with
that statement. Subsequently issuing the prepared statement with
db2_execute() enables the statements to reuse that
access plan and avoids the overhead of dynamically creating a new access
plan for every statement you issue.
Security: when you prepare a statement, you can
include parameter markers for input values. When you execute a prepared
statement with input values for placeholders, the database server checks
each input value to ensure that the type matches the column definition or
Advanced functionality: Parameter markers not only
enable you to pass input values to prepared SQL statements, they also
enable you to retrieve OUT and INOUT parameters from stored procedures
An SQL statement, optionally containing one or more parameter markers..
An associative array containing statement options. You can use this
parameter to request a scrollable cursor on database servers that
support this functionality.
Passing the DB2_FORWARD_ONLY value requests a
forward-only cursor for this SQL statement. This is the default
type of cursor, and it is supported by all database servers. It is
also much faster than a scrollable cursor.
Passing the DB2_SCROLLABLE value requests a
scrollable cursor for this SQL statement. This type of cursor
enables you to fetch rows non-sequentially from the database
server. However, it is only supported by DB2 servers, and is much
slower than forward-only cursors.
Returns a statement resource if the SQL statement was successfully parsed and
prepared by the database server. Returns FALSE if the database server
returned an error. You can determine which error was returned by calling
db2_stmt_error() or db2_stmt_errormsg().
Example 1. Preparing and executing an SQL statement with parameter markers
The following example prepares an INSERT statement that accepts four
parameter markers, then iterates over an array of arrays containing the
input values to be passed to db2_execute().