如何创建每个第n项的数组？

Question

Say I have the following table:

name
----
A
B
C
D
E
F
G
H
I

I can extract this from MySQL and put it in an array:

$result = mysql_query("SELECT * FROM names ORDER BY name DESC");
while ($row = mysql_fetch_object($result)) {
  $names[] = $row->name
}

What I am now looking for is a script that loops through $names and returns pairs, for instance every 3rd name:

array(
  [A] => [C],
  [B] => [D],
  [C] => [E],
  [D] => [F]
  [E] => [G]
  [F] => [H]
  [G] => [I]
)

Or, for instance, every 4th name:

array(
  [A] => [D],
  [B] => [E],
  [C] => [F],
  [D] => [G]
  [E] => [H]
  [F] => [I]
)

The number of names in between (3 in the fist example, 4 in the second) should be variable. Does anybody know how to do this in php?

Answer 1

You can do this using a fairly simple for loop.

Here's an example. All you need to do is tweak $seperation:

<?php

$array = array('A','B','C','D','E','F','G','H','I');
$seperation = 3;
$assoc = array(); // stores result

for($i = 0; $i+$seperation < count($array); $i++) {
   $assoc[$array[$i]] = $array[$i + $seperation];
}

print_r($assoc);

Demo