Thursday, April 12, 2012

How to detect duplicate values in PHP array?


I am working with a one dimensional array in PHP. I would like to detect the presence of duplicate values, then count the number of duplicate values and out put the results. For example, given the following array:




$array = array('apple', 'orange', 'pear', 'banana', 'apple',
'pear', 'kiwi', 'kiwi', 'kiwi');



I would like to print:




apple (2)
orange
pear (2)
banana
kiwi (3)



Any advice on how to approach this problem?



Thanks.



Mike


Source: Tips4all

7 comments:

  1. use array_count_values

    $array = array('apple', 'orange', 'pear', 'banana', 'apple',
    'pear', 'kiwi', 'kiwi', 'kiwi');

    print_r(array_count_values($array));


    will output

    Array
    (
    [apple] => 2
    [orange] => 1
    [pear] => 2
    etc...
    )

    ReplyDelete
  2. if(count(array_unique($array))<count($array))
    {
    // Array has duplicates
    }
    else
    {
    // Array does not have duplicates
    }

    ReplyDelete
  3. to get rid use array_unique. To detect if have any use count(array_unique) and compare to count(original array).

    ReplyDelete
  4. function array_not_unique( $a = array() )
    {
    return array_diff_key( $a , array_unique( $a ) );
    }

    ReplyDelete
  5. Stuff them into a map (pseudocode)

    map[string -> int] $m
    foreach($word in $array)
    {
    if(!$m.contains($word))
    $m[$word] = 0;

    $m[$word] += 1;
    }

    ReplyDelete
  6. Perhaps something like this (untested code but should give you an idea)?

    $new = array();

    foreach ($array as $value)
    {
    if (isset($new[$value]))
    $new[$value]++;
    else
    $new[$value] = 1;
    }


    Then you'll get a new array with the values as keys and their value is the number of times they existed in the original array.

    ReplyDelete
  7. You could try turning that array into a associative array with the fruits as keys and the number of occurrences as values. Bit long-winded, but it looks like:

    $array = array('apple', 'orange', 'pear', 'banana', 'apple',
    'pear', 'kiwi', 'kiwi', 'kiwi');
    $new_array = array();
    foreach ($array as $key => $value) {
    if(isset($new_array[$value]))
    $new_array[$value] += 1;
    else
    $new_array[$value] = 1;
    }
    foreach ($new_array as $fruit => $n) {
    echo $fruit;
    if($n > 1)
    echo "($n)";
    echo "<br />";
    }

    ReplyDelete