CODEWITHSUNDEEP
phparrayssorting
Harpua
Harpua

Reputation: 63

php sort filenames with an underscore

I have an array of filenames that I aquire using DirectoryIterator. I am trying to get the filenames to sort so they would be in order like so, this is the way they appear on the server. 

    2DAYSALEGATE_PG1.jpg
    2DAYSALEGATE_PG2.jpg
    722_PG1.jpg
    PW_PG2_COKE_A.jpg
    PW_PG3_COKE_A.jpg
    PWBY4_DELI-1.jpg

When aquiring the file names they are coming out like this. I have tried to use a sort, natsort and natcasesort. The filename the underscore character is considered after the letters. What can I do to get the underscore to sorted as a priority character.

array(6) {
[0]=>
 string(20) "2DAYSALEGATE_PG1.jpg"
[1]=>
 string(20) "2DAYSALEGATE_PG2.jpg"
[2]=>
 string(11) "722_PG1.jpg"
[5]=>
 string(16) "PWBY4_DELI-1.jpg"
[3]=>
 string(17) "PW_PG2_COKE_A.jpg"
[4]=>
 string(17) "PW_PG3_COKE_A.jpg"
}

Thanks

Upvotes: 3

Views: 1267

Answers (3)

mickmackusa
mickmackusa

Reputation: 47894

Yes, the fact that the underscore appears in the ascii table in a small section of symbols between uppercase letters and lowercase letters is problematic for your desired natural sort.

To move that DELI string higher in the results, temporarily replace the underscores in every string with a space and use natural sorting. The trouble with using 0 as a replacement character is that when the new zero follows another integer, it is effectively multiplying that integer by 10 -- this creates an unreliable sort.

For best efficiency, call str_replace() inside of array_multisort(). This will have a lower time complexity than calling usort(). (usort() will need to call str_replace() twice for at least every element in the array, plus as many times as needed to break ties.)

Code: (Demo)

array_multisort(
    str_replace('_', ' ', $array),
    SORT_NATURAL,
    $array
);

Output:

array (
    0 => '2DAYSALEGATE_PG1.jpg',
    1 => '2DAYSALEGATE_PG2.jpg',
    2 => '722_PG1.jpg',
    3 => 'PWBY4_DELI-1.jpg',
    4 => 'PW_PG2_COKE_A.jpg',
    5 => 'PW_PG3_COKE_A.jpg',
)

Upvotes: 0

Dima
Dima

Reputation: 8652

You can use the php usort method, check it out here with usort you can implement your custom compare to function and sort the array according to it.

the custom compare to function is int callback ( mixed $a, mixed $b ) , you should return a value less than 0 if $a < $b , zero if equal and a value bigger than 0 when $a > $b

implement your preferred order of sorting using this method

example:

function cmp($a, $b) {
  $aTemp = str_replace('_', '0', $a);
  $bTemp = str_replace('_', '0', $b);     
  return strcmp($aTemp,$bTemp);
}

 usort($arr, "cmp");

Upvotes: 7

Anachronist
Anachronist

Reputation: 1102

Not sure what you can do here. Lexically, the underscore has a higher ASCII value than any alphanumeric character.

Replacing the underscore with a low ASCII value like \x01, then sorting, then replacing the low ASCII value with an underscore, will give the result you want, but that seems pretty expensive for a trivial change in order.

Upvotes: 3

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