Using massive PHP memory for SQL query

I ran into an odd problem while optimizing memory usage of Apache + PHP. Basically, the code explodes with the error message "Fatal error: the allowed memory size of 16777216 bytes has been exhausted (tried to allocate 50331646 bytes)" when trying to link the results of a MySQLi query.

Relevant tables:

CREATE TABLE `note` (
  `noteID` int(11) NOT NULL AUTO_INCREMENT,
  `contentID` int(11) NOT NULL,
  `text` mediumtext NOT NULL,
  PRIMARY KEY (`noteID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `content` (
  `contentID` int(11) NOT NULL AUTO_INCREMENT,
  `text` varchar(2048) NOT NULL,
  `datestamp` datetime NOT NULL,
  PRIMARY KEY (`contentID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

and the request that explodes is as follows:

select content.contentID, 
content.text, 
content.datestamp, 
note.noteID, 
note.contentID, note.text 
from basereality.content as content 
inner join basereality.note as note 
on content.contentID = note.contentID 
where content.contentID = 1028 ;

Query execution in MySQL on the server is normal, and the size of the returned "note" is under kilobytes.

, , 50331646, 0x2FFFFFE , . , PHP , , , .

- - , PHP?

btw , , , , . ( 50855936) ( 50331646 )

, , :

$statement->bind_result(
  $content_contentID,
  $content_text,
  $content_datestamp,
  $note_noteID,
  $note_contentID,
  $note_text);

, " " ", .

btw , . mediumtext :

 select length(text) from basereality.note;
+--------------+
| length(text) |
+--------------+
|          938 |
|          141 |
|         1116 |
|          431 |
|          334 |
+--------------+