find duplicates in php bidimensional array

Question

I have a bidimensional array in php like this:

Array (
        [0] => Array
            (
                        [index1] => -1
                        [index2] => 77
                        [description] => 7
                    )
        [1] => Array
            (
                        [index1] => -1
                        [index2] => 77
                        [description] => 5
                    )
        [2] => Array
            (
                        [index1] => -1
                        [index2] => 78
                        [description] => 12
                    )
)

I need to find if there is a duplicate between the first level arrays. But only considering the keys index1 and index2.

In the example above, it should return true because 0 and 1 have the same index1 and index2.

stewe · Accepted Answer · 2012-03-23 22:26:53Z

2

Try this:

<?php

$a=array(
    array('index1'=>-1,'index2'=>77,'description'=>7),
    array('index1'=>-1,'index2'=>77,'description'=>5),
    array('index1'=>-1,'index2'=>78,'description'=>12)
);


function check($a){
    $data=array();

    foreach($a as $arr){
        if ($data[$arr['index1'].'|'.$arr['index2']]) {
            return true;
        }
        $data[$arr['index1'].'|'.$arr['index2']]=true;
    }
    return false;
}

if (check($a)) {
    echo "duplicates found";
}else{
    echo "no duplicates";
}

?>

answered Mar 23, 2012 at 22:26

stewe

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Comments

rik · Accepted Answer · 2012-03-23 22:53:00Z

1

function hasDupes($array, $delim = '|') {
    $values = array();
    foreach ($array as $v) {
        $v = $v['index1'] . $delim . $v['index2'];
        if (isset($values[$v])) {
            return true;
        }
        $values[$v] = 0;
    }
    return false;
}

No need for nested loops or complete walks (or even multiple walks) over the array, which btw is what most of the suggested array_something functions do internally. Iterate once and stop when you see an element that you've seen before.

edited Mar 23, 2012 at 22:53

answered Mar 23, 2012 at 22:26

rik

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2 Comments

stewe Over a year ago

You should use a separator, otherwise array(index1=>-1,index2=>77) and array(index1=>-17,index2=>7) would not work for example.

rik Over a year ago

@stewe thx, added. But actually the delimiter must not be the first or last character otherwise array(index1=>'-1|',index2=>77) and array(index1=>'-1',index2=>'|77') would not work. Anyway ...

Nir Alfasi · Accepted Answer · 2012-03-23 22:12:15Z

0

Two methods that can help you:
1. if you just want to remove the duplicates you can use:
http://php.net/manual/en/function.array-unique.php
2. if you want to find the dups, you can scan the array, and "for each" item - check the rest of the array using:
http://php.net/manual/en/function.array-search.php

answered Mar 23, 2012 at 22:12

Nir Alfasi

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Comments

gapple · Accepted Answer · 2012-03-23 22:20:49Z

0

Not a very efficient algorithm, but the brute force way assuming the outer array is numerically indexed:

function hasDuplicates($array) {
  $count = count($array);
  for ($i = 0; $i < $count; $i++){
    for ($j = $i+1; $j < $count; j++) { // check every later element in the array
      if ($array[i]['index1'] == $array[j]['index1'] && $array[i]['index2'] == $array[j]['index2']) {
        return true;
      }
    }
  }
  return false;
}

answered Mar 23, 2012 at 22:20

gapple

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Comments

worenga · Accepted Answer · 2012-03-23 22:21:27Z

0

Sort the Array using a custom sorting function like http://de3.php.net/manual/de/function.uasort.php
Walk through the sorted array and compare neighbours pairwise, if they are identical return true otherwise false

answered Mar 23, 2012 at 22:21

worenga

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