Description:
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Using mysqli in combination with the prepare-method and bind_param leads to troubles with the BLOB-field. I'm not really sure if it is a bug or I just thinking the wrong way.

Reproduce code:
---------------
<?php
$m = new mysqli( "host, "user", "pass" );
$m->select_db( "my_db" );
if( $statement = $m->prepare( "INSERT INTO my_table SET my_blob = ?" ))
{
   $file = file_get_contents( "image.png" );
   $statement->bind_param( 'b', $file );
   $statement->execute();
}
?>

Expected result:
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Image should be inserted as binary data into the MySQL-table.

Actual result:
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This does not work, it just puts zero bytes into the database. If I change $statement->bind_param( 'b', $file ); to $statement->bind_param( 's', $file ); it works as expected