PHP Memory limit exceeded

Hi all, I got a problem with uploading files which encounter the memory limit when their size is not even close to the memory limit itself, let me explain. My server is as follows: 1. PHP 4.3.9 2. DB - Postgresql 7.4 3. Apache 1.3.26 Here is my code that i made for testing the problem (along the code i echoed the function memory_get_usage() to know how much memory was allocated already for the script):

$imagefile    =    $_FILES['imagefile']; // recieve the file
echo memory_get_usage().'<br />';    // 118592 memory bytes allocated
  $data = pg_escape_bytea(cat $imagefile[tmp_name]);
echo memory_get_usage().'<br />';    // 5570280 memory bytes allocated

$data = "INSERT INTO test_files (bin_data, filename, filesize, filetype) VALUES ('$data', '$imagefile[name]', '$imagefile[size]', '$imagefile[type]')"; // creating the sql for the insert, i called the received value also $data cause i dont want to keep the previous $data (after all we want to save our precious memory no? :))

echo memory_get_usage().'<br />';    // 5570400 memory bytes allocated {changed from b4 only alittle}

if ( !$res = pg_query ($this->conn, $data) ) // try to insert the sql string return 'error'; else return 'gr8';

echo memory_get_usage().'<br />';    // 5570648 memory bytes allocated {again changed only alittle}

Now as far as i see the script needed about 5.5MB of memory to upload a file of 4.7MB but thats what so weird here... i receive the memory limit error even if the php.ini "memory_limit" is set to 16MB! {twice of the default of 8MB!} at 32MB it works fine... but thats way too much.. I suspect that the problem is connected to the pg_query function itself but i didnt find what made it exactly... Any ideas, knowledge or even just solutions ;) will be extremly helpful. Thanks in advance, Ben-Nes Yonatan