# pg_prepare

(PHP 5 >= 5.1.0, PHP 7)

pg_prepare — Submits a request to create a prepared statement with the given parameters, and waits for completion

### 说明

pg_prepare ([ resource `$connection` ], string `$stmtname` , string `$query` ) : resource

pg_prepare() creates a prepared statement for later execution with pg_execute() or pg_send_execute(). This feature allows commands that will be used repeatedly to be parsed and planned just once, rather than each time they are executed. pg_prepare() is supported only against PostgreSQL 7.4 or higher connections; it will fail when using earlier versions.

The function creates a prepared statement named `stmtname` from the `query` string, which must contain a single SQL command. `stmtname` may be "" to create an unnamed statement, in which case any pre-existing unnamed statement is automatically replaced; otherwise it is an error if the statement name is already defined in the current session. If any parameters are used, they are referred to in the `query` as $1, $2, etc.

Prepared statements for use with pg_prepare() can also be created by executing SQL PREPARE statements. (But pg_prepare() is more flexible since it does not require parameter types to be pre-specified.) Also, although there is no PHP function for deleting a prepared statement, the SQL DEALLOCATE statement can be used for that purpose.

### 参数

`connection`

  PostgreSQL database connection resource. When `connection` is not present, the default connection is used. The default connection is the last connection made by pg_connect() or pg_pconnect().

`stmtname`

  The name to give the prepared statement. Must be unique per-connection. If "" is specified, then an unnamed statement is created, overwriting any previously defined unnamed statement.

`query`

  The parameterized SQL statement. Must contain only a single statement. (multiple statements separated by semi-colons are not allowed.) If any parameters are used, they are referred to as $1, $2, etc.

### 返回值

A query result resource on success 或者在失败时返回 `FALSE`.

### 范例

Example #1 Using pg_prepare()

    <?php
    // Connect to a database named "mary"
    $dbconn = pg_connect("dbname=mary");

    // Prepare a query for execution
    $result = pg_prepare($dbconn, "my_query", 'SELECT * FROM shops WHERE name = $1');

    // Execute the prepared query.  Note that it is not necessary to escape
    // the string "Joe's Widgets" in any way
    $result = pg_execute($dbconn, "my_query", array("Joe's Widgets"));

    // Execute the same prepared query, this time with a different parameter
    $result = pg_execute($dbconn, "my_query", array("Clothes Clothes Clothes"));

    ?>

### 参见

- pg_execute() - Sends a request to execute a prepared statement with given parameters, and waits for the result
- pg_send_execute() - Sends a request to execute a prepared statement with given parameters, without waiting for the result(s)