Sort data of Php array by values of another array

Question

I've two PHP Arrays. The first one contains a sort order. The second one contains the data which i need to sort. I have no idea how to solve it…

What I'm trying to get is a list, sorted by the values of the first array (order.txt). Any suggestions?

<li>Item [2]</li>
<li>Item [1]</li>
<li>Item [3]</li>

Order

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

Data

Array
(
    [0] => Array
        (
            [id] => 1
            [name] => 00134258.jpg
            [size] => 2787
        )

    [1] => Array
        (
            [id] => 2
            [name] => 80132454.jpg
            [size] => 2667
        )

    [2] => Array
        (
            [id] => 3
            [name] => 13134218.jpg
            [size] => 2787
        )

)

Here are the code which produces the arrays above:

<?php

    $order = file('order.txt');

    foreach ($order as $key => $value) {
        $order = json_decode($value, true);
    }

    print_r($order);


    $file = file('db.txt');

    foreach ($file as $key => $value) {
        $file_data[] = json_decode($value, true);
    }

    print_r($file_data);
?>

This are the json strings:

order.text

{"0":"2","1":"1","2":"3"}

db.txt

{"id":"1","name":"00134258.jpg","size":2787}
{"id":"2","name":"80132454.jpg","size":2667}
{"id":"3","name":"13134218.jpg","size":2787}

Toolkit: php.net/manual/en/array.sorting.php

Mike B
– Mike B

2011-12-02 21:45:25 +00:00
Commented Dec 2, 2011 at 21:45 — Mike B
– Mike B, Commented Dec 2, 2011 at 21:45

Billy Moon · Accepted Answer · 2011-12-02 22:01:49Z

2

Make a new array where the keys are the id of the data, then loop through your order array and assign the values to an ordered array...

<?php
  // loop through the file data
  foreach($file_data as $v){
    // assign values to new array with the data id as it's key
    $identified[$v['id']] = $v;
  }
  // loop through the order array
  foreach($order as $v){
    // pull the data values from the identified array by their key
    $ordered[] = $identified[$v];
  }
  // check it has all worked out as planned ;)
  print_r($ordered);
?>

Alternatively... in line with @hakre's method, first create array ordered by index, and then use array_multisort method.

<?php
  foreach($file_data as $v){
    $ordered[$v['id']] = $v;
  }
  array_multisort($order, $ordered);
  print_r($ordered);
?>

edited Dec 2, 2011 at 22:01

answered Dec 2, 2011 at 21:54

Billy Moon

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2 Comments

gearsdigital Over a year ago

Thank you very much! But this will only work as long the ids are in chronological order like 1,2,3,4. 1,5,11,44 will not work as i unterstand your code correctly, right?

Billy Moon Over a year ago

I have not tested, but I think it should work with ids that are in any order. The first part, actually puts the data into order according to it's id. It achieves this, by using the id value as the key for the whole row. The second part pulls the values as needed from the now correctly indexed array.

hakre · Accepted Answer · 2011-12-02 21:45:03Z

2

From your $order array substract 1 from each value, then use array_multisort:

foreach($order as &$o) $o--;
unset($o);
array_multisort($order, $data);

This works as long as the id value is always one higher than it's offset in $data.

answered Dec 2, 2011 at 21:45

hakre

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3 Comments

gearsdigital Over a year ago

Thanks for your answer. The & before $o means this is a copy of the array, right?

hakre Over a year ago

No it means that if $o is changed inside the foreach loop, that the original value of it inside $order will be changed. It's a variable alias or reference, see php.net/foreach.

Billy Moon Over a year ago

as soon as one item is deleted from the database, the id may not match

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