pcc at pccglobal dot com (2010-07-30 16:16:45)

When using prepare to prepare a statement to retrieve LOBs the method order matters.
Also, method 'store_result()' must be called and be called in correct order.
Failure to observe this causes PHP/MySQLi to crash or return an erroneous value.
The proper procedure order is: prepare -> execute -> store_result -> bind -> fetch
The following applies to a Windows SBS server running IIS/6.0 + PHP 5.2.1
MySQL server version 5.0.26-community-nt, client version 5.0.51a

<?php
$database = "test" ;
$table = "test" ;
$column = "flongblob" ;
$mysqli = new mysqli("localhost", "root", "<secret_password>", $database);
// Proper procedure order: prepare -> execute -> store_result -> bind -> fetch
$stmt = $mysqli->prepare("SELECT `$column` FROM `$table`") ;
$stmt->execute();
$stmt->store_result(); 
// Fetch a record. Bind the result to a variable called 'value' and fetch.
$stmt->bind_result($value) ;
$res = $stmt->fetch() ;
if($res)
{
  // strlen($value) should have LOB length, not 1 or zero.
  echo "$column data length is " . strlen($value) . " bytes.\n" ;
}
else
{
  echo ((false !== $res) ? "End of data" : $stmt->error) . "\n" ;
  break ;
}
// Fetch another record.
$res = $stmt->fetch() ;
if($res)
{
  // strlen($value) should have LOB length, not 1 or zero.
  echo "$column data length is " . strlen($value) . " bytes.\n" ;
}
else
{
  echo ((false !== $res) ? "End of data" : $stmt->error) . "\n" ;
  break ;
}
$stmt->close() ;
$mysqli->close() ;
exit ;
?>

The above example should output:
  flongblob data length is 932353 bytes.
  flongblob data length is 867300 bytes.

If wrong procedure order MySQLi crashes or outputs:
  flongblob data length is 0 bytes.
  flongblob data length is 867300 bytes.

neromir at hotmail dot com (2008-10-28 19:14:59)

The wording above, in the initial description of the function, can be confusing (quoted below).
"You must call mysqli_stmt_store_result() for every query that successfully produces a result set (SELECT, SHOW, DESCRIBE, EXPLAIN), and only if you want to buffer the complete result set by the client, so that the subsequent mysqli_stmt_fetch() call returns buffered data. "
I had initially understood the part saying "and only if you want to buffer..." to mean that it was only necessary to call this function if you wanted to buffer the result set. This, however, is not the case, and the misunderstanding caused me quite a bit of grief.
So, to clarify for anyone suffering from the same misunderstanding, you ALWAYS must call this function for every query that produces a result set (as listed in the parentheses of the quote above), as far as I can tell.

Typer85 at gmail dot com (2006-12-27 15:58:09)

In response to the note below me for the claim that mysqli_fetch_fields is not compatible with prepared statements.

This is untrue, it is but you have to do a little extra work. I would recommend you use a wrapper function of some sort to take care of the dirty business for you but the basic idea is the same.

Let's assume you have a prepared statement like so. I am going to use the procedural way for simplicity but the same idea can be done using the object oriented way:

<?php

// Connect Blah Blah Blah.

$connectionLink = mysqli_connect( .... );

// Query Blab Blah Blah.

$query = "Select `Id` From `Table` Where `Id` = ?";

// Prepare Query.

$prepareObject = mysqli_prepare( $connectionLink , $query );

// Bind Query.

mysqli_stmt_bind_param( $prepareObject , 'i' , 1 );

// Execute Query.

mysqli_stmt_execute( $prepareObject );

?>

Now all the above is fine and dandy to anyone familiar with using prepared statements, but if I want to use mysqli_fetch_fields or any other function that fetches meta information about a result set but does not work on prepared statements?

Enter the special function mysqli_stmt_result_metadata. It can be used as follows, assume the following code segment immediatley follows that of the above code segment.

<?php

$metaData = mysqli_stmt_result_metadata( $prepareObject );

// I Can Now Call mysqli_fetch_fields using the variable
// $metaData as an argument.

$fieldInfo = mysqli_fetch_fields( $metaData );

// Or Even This.

$fieldInfo = mysqli_num_fields( $metaData );

?>

Take a look at the Manual entry for mysqli_stmt_result_metatdata function for full details on how to expose it with prepared statements.

Good Luck,

UCFirefly (at) yahoo.com (2006-02-20 12:25:33)

fetch_fields() does not seem to be compatible with prepared statements like those used here. Makes things difficult if you're using a wildcard. I guess that's better for security in some obscure way.
-Alex Boese