PDO::pgsqlLOBOpen

(PHP 5 >= 5.1.2, PHP 7, PHP 8, PECL pdo_pgsql >= 1.0.2)

PDO::pgsqlLOBOpen — Opens an existing large object stream

说明

public PDO::pgsqlLOBOpen(string $oid, string $mode = "rb"): resource|false

PDO::pgsqlLOBOpen() opens a stream to access the data referenced by oid. If mode is r, the stream is opened for reading, if mode is w, then the stream will be opened for writing. You can use all the usual filesystem functions, such as fread(), fwrite() and fgets() to manipulate the contents of the stream.

注意: This function, and all manipulations of the large object, must be called and carried out within a transaction.

参数

oid: A large object identifier.
mode: If mode is r, open the stream for reading. If mode is w, open the stream for writing.

返回值

Returns a stream resource on success 或者在失败时返回 false.

示例

示例 #1 A PDO::pgsqlLOBOpen() example

Following on from the PDO::pgsqlLOBCreate() example, this code snippet retrieves the large object from the database and outputs it to the browser.

<?php
$db = new PDO('pgsql:dbname=test host=localhost', $user, $pass);
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$db->beginTransaction();
$stmt = $db->prepare("select oid from BLOBS where ident = ?");
$stmt->execute(array($some_id));
$stmt->bindColumn('oid', $oid, PDO::PARAM_STR);
$stmt->fetch(PDO::FETCH_BOUND);
$stream = $db->pgsqlLOBOpen($oid, 'r');
header("Content-type: application/octet-stream");
fpassthru($stream);
?>

参见

PDO::pgsqlLOBCreate() - Creates a new large object
PDO::pgsqlLOBUnlink() - Deletes the large object
pg_lo_open() - 打开大对象

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User Contributed Notes 3 notes

down

binaryexp at gmail ¶

14 years ago

This is what worked for me. If you have the oid, then all you need to do is:

<?php
$pdo = new PDO($dsn, $user, $pass);
$pdo->beginTransaction();
$data = $pdo->pgsqlLOBOpen($oid, 'r');

header("Content-Type: $mime");
// any other headers...

fpassthru($data);  // echo stream_get_contents($data); also works
?>

The beginTransaction() is required, if you want to $pdo->commit() (it's not required) then do it after the fpassthru.

On a side note, those using Zend Framework can call getConnection() on the standard PDO database object which will get them the $pdo object as above. Then just remember to disableLayout() and setNoRender() as necessary.

down

knl at bitflop dot com ¶

15 years ago

Also remember that fread() will only parse the first 8192 bytes from the stream. Use..

<?php
$data = stream_get_contents($stream);
?>

.. if you have a larger output to parse.

down

knl at bitflop dot com ¶

15 years ago

The above example is missing some data. After spending several hours trying to get it to work in vain, Jeff Davis from the PostgreSQL channel on IRC (freenode) figured out what was missing.

The below example will work, but you have to insert the MIME type and file size of the large object that you are storing, so you can use that data for extraction.

<?php
$db = new PDO('pgsql:dbname=test host=localhost', $user, $pass);
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$db->beginTransaction();
$stmt = $db->prepare("SELECT oid, blob_type, filesize FROM BLOBS WHERE ident = ?");
$stmt->execute(array($some_id));
$stmt->bindColumn('oid', $lob, PDO::PARAM_LOB);
$stmt->bindColumn('blob_type', $blob_type, PDO::PARAM_STR);
$stmt->bindColumn('filesize', $filesize, PDO::PARAM_STR);
$stmt->fetch(PDO::FETCH_BOUND);
$stream = $pdo->pgsqlLOBOpen($lob, 'r');
$data = fread($stream, $filesize);
header("Content-type: $blob_type");
echo $data;
?>

Also fpassthru() will just give this result: Warning: fpassthru(): supplied argument is not a valid stream resource in ...

Use echo or print instead.

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