How to sort array from file (PHP)? - php

Question

I have a file here which contains list of database names and its corresponding size.
Now I want to sort the size from the largest to the lowest, and the database name
should go along it upon display.Am using PHP here..
Can anyone help me out?
Here's a simple code for that:
$file_name = test.txt
$handle = #fopen($file_name, "r");
if ($handle) {
while (!feof($handle)) {
$buffer = fgets($handle, 4096);
$data = explode(" ",$buffer);
echo $data[1]."\n";
}
fclose($handle);
}
File looks like this:
DatabaseName 300 KB
Note: $data[1] contains the sizes. Should i place it on an array? how about the db name?
Answers are very much appreciated. =)

Answer 1

First you need to build an array with an element you can actually sort on, then use usort or similar to perform the sort based on your custom criteria.
//first build up an array of databases with a unified size in bytes, ensuring
//we account for those postfixes like KB,MB,and GB
$databases=array();
while (!feof($handle)) {
$buffer = fgets($handle, 4096);
$data = explode(" ",$buffer);
if (count($data)==3)
{
$size=$data[1];
switch ($data[2])
{
case 'KB': $size*=1024; break;
case 'MB': $size*=1024*1024; break;
case 'GB': $size*=1024*1024*1024; break;
}
$data[3]=$size;
$databases[]=$data;
}
else
{
die("Bad line in file: $buffer");
}
}
Now sort with a custom comparison function to sort from high to low based on that calculated size:
function cmp($a, $b)
{
if ($a[3] == $b[3]) {
return 0;
}
return ($a[3] < $b[3]) ? 1 : -1;
}
usort($databases, "cmp");

Answer 2

You can use the file() PHP function here.
Your text file is like :
DatabaseName 300 KB
DatabaseName 300 KB
DatabaseName 300 KB
DatabaseName 300 KB
I think you can use the PHP native function on arrays.
$data = file('myfile.txt');
foreach($data as $one_line)
{
$db[] = explode(" ",$one_line)
//will have $db[0][0] = 'dbname';
//will have $db[0][2] = '30';
//will have $db[0][2] = 'KB';
//will have $db[1][0] = 'dbname';
//will have $db[1][3] = '30';
//will have $db[1][2] = 'KB';
}
array_multisort($db[1], SORT_NUMERIC, SORT_DESC);
See this comment in documentation, the same structure : http://fr2.php.net/manual/en/function.array-multisort.php#79491
Or maybe you have to flip the array, so you can have size in index and name in value.

Answer 3

function databases_sort($a, $b) {
if ($a[1] == $b[1]) { return 0; }
return ($a[1] < $b[1]) ? -1 : 1;
}
$file_name = "test.txt";
$handle = #fopen($file_name, "r");
$databases = array();
if ($handle) {
while (!feof($handle)) {
$buffer = fgets($handle, 4096);
$data = explode(" ",$buffer);
$databases[] = $data;
//echo $data[1]."\n";
}
usort($databases, "databases_sort");
foreach ($databases as $d) {
echo $d[1];
}
fclose($handle);
}
This code stores your information in an array, then runs a custom sorting function on your array, sorting it by the value of element 1 in the array. Higher values (larger database sizes) get sorted to the top of the list.
Warning: I haven't actually tested this code, but you can see the usort documentation if there are any bugs that need fixing.
Edit: d'oh, beaten by a few seconds :-)

Answer 4

Have you thought about parsing into a binary search tree structure instead of an array? That way you could have the data sorted with a tree traversal and you could have fast lookup too.