ODBC 函数
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odbc_longreadlen

(PHP 4, PHP 5)

odbc_longreadlen — Handling of LONG columns

说明

bool odbc_longreadlen ( resource $result_id , int $length )

Enables handling of LONG and LONGVARBINARY columns.

参数

result_id

The result identifier.

length

The number of bytes returned to PHP is controlled by the parameter length. If it is set to 0, Long column data is passed through to the client.

返回值

成功时返回 TRUE， 或者在失败时返回 FALSE.

注释

Note:

Handling of LONGVARBINARY columns is also affected by odbc_binmode().

ODBC 函数
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PHP手册 - N: Handling of LONG columns

用户评论:

egil at wp dot pl (22-Jul-2009 10:06)

I've tried to use a suggestion in the first comment but that didn't actually worked as I would expect... I wanted to get all data no matter how big it is, but strange things happened and I finally found this solution (works fine at least for MS SQL 2000 for at least few MB of binary data):

<?php
// connection
$link = odbc_connect($odbc_source_name, $user, $pass);

// query (note - one row in this example)
$sql = 'SELECT image_data_column FROM some_table WHERE record_id=1';

// run
$result = odbc_exec ($link, $sql)
if (!$result)
{
    trigger_error ('[sql] exec: '.$sql, E_USER_ERROR);
}

// fetch settings
odbc_binmode ($result, ODBC_BINMODE_PASSTHRU);
odbc_longreadlen ($result, 0);

// get contents
ob_start(); // you would probably need to move this inside if you expect more rows
while (odbc_fetch_row($result))
{
    odbc_result($result, 1); // this actually echos all of the contents of the image_data_column
}
odbc_free_result($result);
$contents = ob_get_clean();
?>

Paul Schmidinger (30-Aug-2005 01:44)

In my current situation, odbc_binmode(), odbc_longreadlen() and the lrl-setting in the php.ini do not help. But when I remove the DISTINCT from my SELECT-query, it works. I guess in my case DISTINCT truncates the data somehow. Hope that helps someone.

Paul

php dot net dot notes at webqs dot com (06-Aug-2005 02:12)

Hi

If you are experiencing troubles with truncated and/or strangely encoded data when using PHP with MS SQL via ODBC try setting odbc.defaultlrl ( in php.ini or via ini_set() ) to a largish number, say 65536, as stated in the other notes here.
The trick is to know how long your data is going to be, so you may want to provide some overhead. Unfortunately you have to know how long your piece of string is before you cut it.

Doing this will allow your app to read up to this amount in one go. I'm sure there is a reason for this behaviour but I hadn't experienced anything like it in 5 years of MySQL and Postgres development.

If you still experience problems AND are using unicode data in the long column of your table, make sure it is set to type "ntext", if it is "text". MSDN has some info on data types for Unicode data.
This caused about 3 days of headaches for me, "binary" data crashing browsers and cyclical result sets (i.e repeating data after odbc.defaultlrl bytes).

This fix was only found by poking things with sticks.

HTH

jdcard at inreach dot com (09-Dec-2004 05:37)

I was reading from a MEMO field (long varchar) in MSAccess, but the data was consistently truncated at 255 characters. I tried all the combinations of odbc_longreadlen() and odbc_binmode()  (and odbc.defaultlrl) that I could think of but none of them resolved the problem.

The only fix that worked was to modify my query from "SELECT Field1, Field2 FROM TableName" to "SELECT * FROM TableName".

I suspect that you could cast the field to force the appropriate data type, but when it finally worked after three days of struggle I didn't even try.

(26-Sep-2002 01:00)

An alternative is to adjust your php.ini file and set:
odbc.defaultlrl=65536
Or something else sufficiently large.
lrl = long read length

buzz77 at gmx dot net (23-Nov-2001 10:31)

Aaargh!
I was wondering about truncated data when reading from a TEXT (LONG VARCHAR) column.
With this I was able to increase the buffer size...

jasendorf at lcounty dot com (14-Dec-2000 12:26)

I had a heck of a time figuring out what to do with this function.  Here's a little piece of code from Jason Lee which I found that might help someone else...

$cur = odbc_exec($cnx, $query);
if(!$cur) {
/* error handler */
}

odbc_binmode($cur, ODBC_BINMODE_PASSTHRU);
odbc_longreadlen($cur, 16384); /* Allow 16kb thru */

while(odbc_fetch_row($cur)) {
$bigger_than_4096_var = odbc_result($cur, 1);
/* etc... */

Hope this helps someone, John