[PHP] Multidimensional arrays, Memory exhausted From: * R&zE: (renze <email protected>)
Date: 10/08/01

Hi there,

Can anyone tell me why arrays cause such a problem in PHP?

I've got a tab separated file that I want to process. When I read
it in memory PHP gives me an error that the allowed memory size is
exhausted:

Allowed memory size of <size> bytes exhausted ....

The construction I use is that I open the file and use fgetcsv to
read the "records". This returns a 1D array for each record. I add
that record/array to an array (2D) in which I store the complete
contents of the file. So... something like:

$total = array();
$one_record = array();
while ($one_record = fgetcsv ($fd, $max_length, $delimiter)) {
  array_push ($total, $one_record);
}

The file I try to read is 1.5M, contains 9040 lines and each line
contains 85 "columns".
Using the 2D construction described above, PHP requires up to 32M as
the memory_limit. And even then, after testing it several times,
that isn't enough. So... My conclusion is that PHP can't really
handle multidimensional arrays very well.

Reading the complete file into memory using file(), doesn't give any
problems. I can set the memory_limit downto 3M and it still works
fine.

When I use the fgetcsv() construction described above, I can get it
to work though... But I have to make a minor change for that:

array_push ($total, implode ("\t", $one_record));

That's right... I have to make it a 1D array!!! Then there's nothing
wrong.

When I use file() and then try to make a 2D array... it doesn't work
either:

$contents = file ();
foreach ($contents as $record) {
  $data = split ("\t", $record);
  array_push ($total, $data);
}

This also produces the memory exhausted error.

Some other way to try and process this file (and a dirty one it is!)
is by creating all separate 1D arrays:

$var_name = "myVar_$counter";
$$var_name = $data;
$counter++;

But.... No! Doesn't work. All of a sudden PHP doesn't want to work
with the 1D arrays neither.

Can anyone tell me more about this array-bug in PHP? Or even
better... Does anyone know something about a patch for this? 

-- 

* R&zE:

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