How to detect duplicate values in PHP array?

问题:

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

回答1:

You can use array_count_values function

$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...
)

回答2:

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

回答3:

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

回答4:

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

回答5:

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 />";
}

回答6:

<?php

$arr = array(1, 2, 3, 2, 5, 6, 7);

print_r(array_count_values($arr));

?>

回答7:

Stuff them into a map (pseudocode)

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

    $m[$word] += 1;
}

回答8:

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.

回答9:

$count = 0;
$output ='';
$ischeckedvalueArray = array();
for ($i=0; $i < sizeof($array); $i++) {
    $eachArrayValue = $array[$i];
    if(! in_array($eachArrayValue, $ischeckedvalueArray)) {
        for( $j=$i; $j < sizeof($array); $j++) {
            if ($array[$j] === $eachArrayValue) {
                $count++;
            }
        }
        $ischeckedvalueArray[] = $eachArrayValue;
        $output .= $eachArrayValue. " Repated ". $count."<br/>";
        $count = 0;
    }

}

echo $output;

回答10:

I didn't find the answer I was looking for, so I wrote this function. This will make an array that contains only the duplicates between the two arrays, but not print the number of times an element is duplicated, so it's not directly answering the question, but I'm hoping it'll help someone in my situation.

function findDuplicates($array1,$array2)
{
    $combined = array_merge($array1,$array2);
    $counted = array_count_values($combined);
    $dupes = [];
    $keys = array_keys($counted);
    foreach ($keys as $key)
    {   
        if ($counted[$key] > 1)
        {$dupes[] = $key;}
    }
    sort($dupes);
    return $dupes;
}
$array1 = [1,2,3,4,5];
$array2 = [4,5,6,7,8];
$dupes = findDuplicates($array1,$array2);
print_r($dupes);

Outputs:

Array
(
    [0] => 4
    [1] => 5
)