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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()


add a note add a note User Contributed Notes
william dot clarke at gmail dot com
01-Sep-2006 06:58
Surely if you want to use prepared statements that way you should use the syntax in the second example:

eg.

instead of:
select id,name from demo_de where name LIKE :name OR name=:name

use:
select id,name from demo_de where name LIKE ? OR name=?

I believe you are supposed to either use distinct named parameters (name, name1) OR anonymous parameters (?s)
roth at egotec dot com
30-Aug-2006 04:58
Attention using MySQL and prepared statements.
Using a placeholder multiple times inside a statement doesn't work. PDO just translates the first occurance und leaves the second one as is.

select id,name from demo_de where name LIKE :name OR name=:name

You have to use

select id,name from demo_de where name LIKE :name OR name=:name2

and bind name two times. I don't know if other databases (for example Oracle or MSSQL) support multiple occurances. If that's the fact, then the PDO behaviour for MySQL should be changed.
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