Converting a string to a set of array with fixed length

Question

I need to convert a string into a set of arrays of a fixed length.

Example: input: 1111122222333333

I need output of

[0] =>
    [0] => 1
    [1] => 1
    [2] => 1
    [3] => 1
    [4] => 1
[1] =>
    [0] => 2
    [1] => 2
    [2] => 2
    [3] => 2
    [4] => 2

The following code works great:

    for ($x = 0; $x < count($codedDataArray) - $colWidthSum + 1; $x += $colWidthSum + 1) {

        for ($c = 0; $c <= $colWidthSum; $c++) {
            $rows[$j][] = $codedDataArray[$z];
            $z++;
        }
        $j++;
    }

but it runs out of memory when I give it really large strings, say 10959 bytes.

Is there a built-in PHP function I'm missing that will do the same thing, or am I just going to have to deal with the memory issues?

EDIT 1: I'm running out of memory on both preg_split and str_split as well, so I'm probably doing something really wrong. I'll still mark as answered, as soon as I figure out what my initial issue was in the first place.

EDIT 2: The string length is actually 745,982 bytes, I was looking at the compressed length.

EDIT 3: I think the string is just too big. I'll have to see if there as a way of breaking it up without losing data since that's actually a small example and it's actually binary data. Thanks for the answers everyone!

runs out of memory. Works find on a stream of length 137, so I don't think it's a loop. — Drazisil
– Drazisil, Commented Jun 20, 2011 at 17:35

Damien Pirsy · Accepted Answer · 2011-06-21 03:48:46Z

14

Try this. I've just tested with a string of 10,000 words and it didn't run out of memory:

$array = str_split($string);

// returns $array = Array
(
    [0] => 1
    [1] => 1
    [2] => 1
    [3] => 1
    [4] => 1
    [5] => 2
    [6] => 2
    [7] => 2
    [8] => 2
    [9] => 2
    [10] => 3
    [11] => 3
   // and so on
)

Then:

array_chunk($array, 5);

// returns:

[0] => Array
    (
        [0] => 1
        [1] => 1
        [2] => 1
        [3] => 1
        [4] => 1
    )

[1] => Array
  (
        [0] => 1
        [1] => 2
        [2] => 2
        [3] => 2
        [4] => 2
    )

edited Jun 21, 2011 at 3:48

user212218

answered Jun 20, 2011 at 17:42

Damien Pirsy

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Comments

r3c · Accepted Answer · 2011-06-21 04:35:04Z

3

The str_split function might help you, but you'll have to handle the last chunk yourself.

edited Jun 21, 2011 at 4:35

user212218

answered Jun 20, 2011 at 17:33

r3c

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2 Comments

Drazisil Over a year ago

That looked promising, but that runs out of memory as well.

r3c Over a year ago

To be more specific, your sample output needs two splits, you can get it with something like array_map ('str_split', str_split ($str, $length)). If if runs out of memory, then you may want to raise your PHP "max_memory" limit setting.

cwallenpoole · Accepted Answer · 2011-06-20 17:56:05Z

You're not missing something, this is not something built-in. PHP is great at parsing strings, but it can have difficulties with large inputs.

If you know the length of the chunks (and it looks like you do):

// Breaks the strink into $chunkLength sized pieces.
$arr = str_split($input, $chunkLenght);
// str_split all of the chunks:
// explode technically is more historic, but str_split is easier.
array_walk($arr, 'str_split');

If you don't know the chunk size, you'll need to figure that out:

$sizes = array();
$current = FALSE;
$len = count($input);
$curCount = 0;

for($i = 0; $ < $len; $i++){
    if($current != $input[$i]) {
        $current = $input[$i];
        $sizes[$current] = $curCount;
        $curCount = 0;
    }
    $curCount++;
}

function get_filled_array($num, $count) {
     return arrat_pad(array(), $count, $num);
}
$output = array();

foreach($sizes as $index => $count) {
    $output[$index] = get_filled_array($index, $count);
}

VAShhh · Accepted Answer · 2011-06-21 04:34:23Z

1

Use something like

$str = '1111122222333333';
$result = array_chunk(str_split($str), 5);
print_r($result);

Anyways, one way to handle out-of-memory errors can be the creation of a php script that only imlements your internal "for loop" and then call an PHP exec inside the biggest loop.

This will cause the process to launch a thread for each "looping job" without overflowing the memory

edited Jun 21, 2011 at 4:34

user212218

answered Jun 20, 2011 at 17:46

VAShhh

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2 Comments

Drazisil Over a year ago

I think I may have to go the php exec route unless I can figure out what is causing the modem issues. I could expand the max memory, but that just means I'm willing to accept I have poor code.

Jason McCreary Over a year ago

This is a poor use of preg_split() as you don't need the regular expression. str_split() does the same thing in this case and would be better performing. It was already suggested by Damien Pirsy.

Adithya Surampudi · Accepted Answer · 2011-06-20 17:41:29Z

0

Push substrings to the array

$result = array();
for ($index=0; $index<=strlen($string)-$width; $index+= $width)
{
array_push($result,substr($string,$index,$width));
}

answered Jun 20, 2011 at 17:41

Adithya Surampudi

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