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Chapter 8: Databases
Placeholders
Just as
printf( )
builds a string by inserting values into a template, the PEAR DB can
build a query by inserting values into a template. Pass the
query( )
function SQL with
?
in place of specific values, and add a second parameter consisting of the array of
values to insert into the SQL:
$result = $db->query(
SQL
,
values
);
For example, this code inserts three entries into the
movies
table:
$movies = array(array('Dr No', 1962),
array('Goldfinger', 1965),
array('Thunderball', 1965));
foreach ($movies as $movie) {
$db->query('INSERT INTO movies (title,year) VALUES (?,?)', $movie);
}
There are three characters that you can use as placeholder values in an SQL query:
?
A string or number, which will be quoted if necessary (recommended)
|
A string or number, which will never be quoted
&
A filename, the contents of which will be included in the statement (e.g., for
storing an image file in a BLOB field)
Prepare/Execute
When issuing the same query repeatedly, it can be more efficient to compile the
query once and then execute it multiple times, using the
prepare( )
,
execute( )
, and
executeMultiple( )
methods.
The first step is to call
prepare( )
on the query:
$compiled = $db->prepare(
SQL
);
This returns a compiled query object. The
execute( )
method fills in any placehold-
ers in the query and sends it to the RDBMS:
$response = $db->execute(
compiled
,
values
);
The
values
array contains the values for the placeholders in the query. The return
value is either a query response object, or
DB_ERROR
if an error occurred.
For example, we could insert multiple values into the
movies
table like this:
$movies = array(array('Dr No', 1962),
array('Goldfinger', 1965),
array('Thunderball', 1965));
$compiled = $q->prepare('INSERT INTO movies (title,year) VALUES (?,?)');
foreach ($movies as $movie) {
$db->execute($compiled, $movie);
}
,ch08.16110 Page 198 Wednesday, March 13, 2002 11:44 AM

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