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 application:
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 parameter definition.
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 using db2_bind_param().
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().