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# PDO::prepare

(no version information, might be only in CVS)

PDO::prepare -- Prepares a statement for execution and returns a statement object

## 说明

PDOStatement PDO::prepare ( string statement [, array driver_options] )

Prepares an SQL statement to be executed by the PDOStatement::execute() method. The SQL statement can contain zero or more named (:name) or question mark (?) parameter markers for which real values will be substituted when the statement is executed. You cannot use both named and question mark parameter markers within the same SQL statement; pick one or the other parameter style.

Calling PDO::prepare() and PDOStatement::execute() for statements that will be issued multiple times with different parameter values optimizes the performance of your application by allowing the driver to negotiate client and/or server side caching of the query plan and meta information, and helps to prevent SQL injection attacks by eliminating the need to manually quote the parameters.

PDO will emulate prepared statements/bound parameters for drivers that do not natively support them, and can also rewrite named or question mark style parameter markers to something more appropriate, if the driver supports one style but not the other.

## 参数

statement

  This must be a valid SQL statement for the target database server.

driver_options

  This array holds one or more key=>value pairs to set attribute values for the PDOStatement object that this method returns. You would most commonly use this to set the PDO_ATTR_CURSOR value to PDO_CURSOR_SCROLL to request a scrollable cursor. Some drivers have driver specific options that may be set at prepare-time.

## 返回值

If the database server successfully prepares the statement, PDO::prepare() returns a PDOStatement object.

## 范例

例子 1. Prepare an SQL statement with named parameters

`<?php
/* Execute a prepared statement by passing an array of values */
$sql = 'SELECT name, colour, calories
FROM fruit
WHERE calories < :calories AND colour = :colour';
$sth = $dbh->prepare($sql, array(PDO_ATTR_CURSOR, PDO_CURSOR_FWDONLY));
$sth->execute(array(':calories' => 150, ':colour' => 'red'));
$red = $sth->fetchAll();
$sth->execute(array(':calories' => 175, ':colour' => 'yellow'));
$yellow = $sth->fetchAll();
?>`

例子 2. Prepare an SQL statement with question mark parameters

`<?php /* Execute a prepared statement by passing an array of values */ $sth = $dbh->prepare('SELECT name, colour, calories FROM fruit WHERE calories < ? AND colour = ?'); $sth->execute(array(150, 'red')); $red = $sth->fetchAll(); $sth->execute(array(175, 'yellow')); $yellow = $sth->fetchAll(); ?>`

## 参见

PDO::exec()
PDO::query()
PDOStatement::execute()

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