Remove dupes/sort from a Array of Associative Arrays in PHP

Question

I have a array of associative arrays

aa[] = ('Tires'=>100, 'Oil'=>10, 'Spark Plugs'=>4 );
aa[] = ('Tires'=>454, 'Oil'=>43, 'Spark Plugs'=>3 );
aa[] = ('Tires'=>34,  'Oil'=>55, 'Spark Plugs'=>44 );
aa[] = ('Tires'=>454, 'Oil'=>43, 'Spark Plugs'=>45 );
aa[] = ('Tires'=>34,  'Oil'=>55, 'Spark Plugs'=>433 );
aa[] = ('Tires'=>23,  'Oil'=>33, 'Spark Plugs'=>44 );

Two Questions

1. How can I remove duplicates according tot he field 'Oil' is there a array_unique which I can provide a callback which acts as a custom comparator?

2. How can I sort by a custom field 'Spark Plugs'

Answer 1

1. I don't know of a function you can use to do this. You will have to do a foreach over the values of the array and do the uniqueness checking manually.

2. Use the usort() function and provide a custom comparator.

Answer 2

For question 1, I think array_filter is what you need.

And, like Brian says, usort for your second question.

Answer 3

Instead of manually going and doing the usual duplicate checking, I did this

$aa2 = array()

foeach($aa as $key => $value)  {
  $aa2[$value['Oil']] = $value;
}
$aa = $aa2;

Then sorting was done by the key...

Answer 4

The issue with remove dupes this way, is how do you determine which values remain, since you're talking about partial uniqueness.

This solution below just keeps the first to appear in index-order. It's not exactly elegant, but it works.

<?php

$aa = array();
$aa[] = array('Tires'=>100, 'Oil'=>10, 'Spark Plugs'=>4 );
$aa[] = array('Tires'=>454, 'Oil'=>43, 'Spark Plugs'=>3 );
$aa[] = array('Tires'=>34,  'Oil'=>55, 'Spark Plugs'=>44 );
$aa[] = array('Tires'=>454, 'Oil'=>43, 'Spark Plugs'=>45 );
$aa[] = array('Tires'=>34,  'Oil'=>55, 'Spark Plugs'=>433 );
$aa[] = array('Tires'=>23,  'Oil'=>33, 'Spark Plugs'=>44 );

echo '<pre>';
print_r( arrayUniqeBySubKey( $aa, 'Oil' ) );
echo '</pre>';

function arrayUniqeBySubKey( $array, $key )
{
  $indexAggregates = array();

  foreach ( $array as $idx => $subArray )
  {
    $indexAggregates[$subArray[$key]][] = $idx;
  }

  foreach ( $indexAggregates as $originalIndexes )
  {
    $numOriginals = count( $originalIndexes );
    if ( 1 == $numOriginals )
    {
      continue;
    }
    for ( $i = 1; $i < $numOriginals; $i++ )
    {
      unset( $array[$originalIndexes[$i]] );
    }
  }
  return $array;
}