Check if array contains a duplicate value in string with PHP

Question

I want to check if my array contains a duplicate value. I have a form where i pass a Chapter ID with the following method:

<input name="chapter_id[]" type="number" value="<?= $row_chapter_list['chapter_id'] ?>">

To update my database i pick this input and do the update w/o any issues:

if (isset($_POST['chapter_id'])) {
 
  // Update Kapitelnummer
  $statement = $pdo->prepare("UPDATE questionaire_chapter SET chapter_id = :chapter_id WHERE id = :id");
  $statement->bindParam(":chapter_id", $chapter_id, PDO::PARAM_STR);
  $statement->bindParam(":id", $id, PDO::PARAM_INT);
  foreach ($_POST['chapter_id'] as $index => $chapter_id) {
    $id = $_POST['chapter_inc_id'][$index];
    $statement->execute();
  }     
}

A typical var_dump result looks like:

array(3) { [0]=> string(1) "1" [1]=> string(2) "12" [2]=> string(2) "12" }

In this array example the value "12" is present in two strings. I would like to create a mechanic to count double values and and use the result in a PHP if/else. i want to avoid that the a duplicate chapter ID gets written into my database.

My first try to count the string is this:

print_r(array_count_values($_POST['chapter_id']));

Which gives me a result like this

Array ( [1] => 1 [12] => 2 )

Now i am missing the method to implement a if else to check if the result is not 1. Any idea how to do this?

Can't you just filter away the duplicates with array_unique()? — M. Eriksson
– M. Eriksson, Commented Jan 10, 2022 at 13:03
No because if there is a duplicate i will not initiate my Update query and give a warning to the user. Is there any function like "if is not unique" ? — Mischa Mustermann
– Mischa Mustermann, Commented Jan 10, 2022 at 13:05
You could do: if ($array != array_unique($array)) { echo "there are duplicates"; } — M. Eriksson
– M. Eriksson, Commented Jan 10, 2022 at 13:09
Thank you! thats exaclty what i was looking for. Please make the answer. — Mischa Mustermann
– Mischa Mustermann, Commented Jan 10, 2022 at 13:11

M. Eriksson · Accepted Answer · 2022-01-10 13:13:52Z

2

You can use array_unique() to get an array where any duplicates has been filtered out. Using that, you can compare it to the original array:

if ($array != array_unique($array)) {
    echo "The arrays are not the same, which means that there are duplicates";
}

answered Jan 10, 2022 at 13:13

M. Eriksson

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1 Comment

Mischa Mustermann Over a year ago

$array = $_POST['chapter_id']; To make it complete ;)

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