Opens a stream resource to read a BLOB

说明

public SQLite3::openBlob(
    string $table,
    string $column,
    int $rowid,
    string $database = "main",
    int $flags = SQLITE3_OPEN_READONLY
): resource|false

Opens a stream resource to read or write a BLOB, which would be selected by:

SELECT column FROM database.table WHERE rowid = rowid

注意: It is not possible to change the size of a BLOB by writing to the stream. Instead, an UPDATE statement has to be executed, possibly using SQLite's zeroblob() function to set the desired BLOB size.

参数

table: The table name.
column: The column name.
rowid: The row ID.
database: The symbolic name of the DB
flags: Either SQLITE3_OPEN_READONLY or SQLITE3_OPEN_READWRITE to open the stream for reading only, or for reading and writing, respectively.

返回值

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

更新日志

版本	说明
7.2.0	The `flags` parameter has been added, allowing to write BLOBs; formerly only reading was supported.

示例

示例 #1 SQLite3::openBlob() example

<?php
$conn = new SQLite3(':memory:');
$conn->exec('CREATE TABLE test (text text)');
$conn->exec("INSERT INTO test VALUES ('Lorem ipsum')");
$stream = $conn->openBlob('test', 'text', 1);
echo stream_get_contents($stream);
fclose($stream); // mandatory, otherwise the next line would fail
$conn->close();
?>

以上示例会输出：

Lorem ipsum

示例 #2 Incrementally writing a BLOB

<?php
$conn = new SQLite3(':memory:');
$conn->exec('CREATE TABLE test (text text)');
$conn->exec("INSERT INTO test VALUES (zeroblob(36))");
$stream = $conn->openBlob('test', 'text', 1, 'main', SQLITE3_OPEN_READWRITE);
for ($i = 0; $i < 3; $i++) {
    fwrite($stream,  "Lorem ipsum\n");
}
fclose($stream);
echo $conn->querySingle("SELECT text FROM test");
$conn->close();
?>

以上示例会输出：

Lorem ipsum
Lorem ipsum
Lorem ipsum