pg_prepare() returns a query result resource if query could be prepared. It returns FALSE on failure or if connection is not a valid connection. Details about the error can be retrieved using the pg_last_error() function if connection is valid. pg_prepare() prepares an SQL statement for the PostgreSQL database connection specified by the connection resource. The connection must be a valid connection that was returned by pg_connect() or pg_pconnect(). The return value of this function is an query result resource. The stmtname is the name of the prepared query, for future use with pg_execute() or pg_send_execute().
Although connection can be omitted, it is not recommended, since it could be a cause of hard to find bug in script.
Parameters to pg_prepare() are specified using placeholders in the query. It is not necessary to quote parameters as quoting and escaping is done automatically. Placeholders are indicated in the query by $1, $2, $3 and so on.
Using prepared queries means you can prepare one and then execute many times, with different parameters. PostgreSQL will cache the query plan on the prepare, then re-use it for each execute, resulting in speed improvements. There is no need to use a prepared query if it will only be executed once. In this case, it is simpler to use pg_query_params().
Exemple 1. Using pg_prepare()