Merge two-dimensional arrays in PHP

Question

I have two two-dimensional arrays (actually they are nested associative arrays) with predefined struture: $array1 and $array2. First array lists all objects by their id numbers:

$array1 = array(
    array(id => 1),
    array(id => 2),
    array(id => 3),
    array(id => 4),
    array(id => 5)
);

The second array lists relationships between objects (e.g., object 2 is connected to objects 3, 4, and 5):

$array2 = array(
    array(id1 => 1, id2 => 2),
    array(id1 => 2, id2 => 3),
    array(id1 => 2, id2 => 4),
    array(id1 => 2, id2 => 5)
);

The aim is to replace id values from the $array2 with corresponding indices from $array1. So, in my case the result should be:

0 1 // index of value 1 (id1) in $array1 is 0, index of 2 (id2) is 1
1 2
1 3
1 4

Pasted below is my current work. First of all I "convert" $array1 to one-dimensional array:

foreach ($array1 as $row) {
    $array3[] = $row['id'];
}

Then I use array_search function and go through $array2 and search the $array3 for a given value and returns the corresponding key in $array3:

foreach ($array2 as $row) {
  $value1 = $row['id1'];
  $key1 = array_search($value1, $array3);
  echo $key1;
  echo "\t";
  $value2 = $row['id2'];
  $key2 = array_search($value2, $array3);
  echo $key2;
  echo '<br />';
}

My question is straightforward: is there a more elegant way to do that (i.e., without using array_search function).

Many thanks in advance for any ideas.

Best, Andrej

Thai · Accepted Answer · 2011-02-02 17:00:38Z

1

You can use an associative array that associates the value to the index.

foreach ($array1 as $index => $row) {
    $array3[$row['id']] = $index;
}

Then you can

$key1 = $array3[$value1];

and

$key2 = $array3[$value2];

answered Feb 2, 2011 at 17:00

Thai

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Comments

Xavier Barbosa · Accepted Answer · 2011-02-02 17:09:16Z

1

if each row in $array1 have an unique id, you can flip the $array3

<?php
$array3 = array();
foreach ($array1 as $k => $v) {
    $array3[$v['id']] = $k;
}
foreach ($array2 as $row) {
    list($id1, $id2) = $row;
    printf("%s\t%s<br />",  $array3[$id1], $array3[$id2]); 
}

answered Feb 2, 2011 at 17:09

Xavier Barbosa

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1 Comment

Andrej Over a year ago

Thanks; nice solutions using list function in the second loop.

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