如果已经在输入值中，如何回显值？

Question

I have some values in a custom field:

save_post = "1200" 

Or it could be, since I need a list eventually:

save_post = "1200, 1460, 1334"

Now when I load the page, I get these values and I set them in an input field, and I also add the current value id from the current page:

$allPosts = $userPosts.", ".$postid;

Where $userPostsis the single value or the value list from the custom field, and $postid is the current page id I want to add.

The result is:

<input type="text" value="1200, 23138, 23138, 23138">

I would always get duplicate values each time I hit the update submit button as the page refreshes itself:

<form id="saveId" action="" method="POST" class="" autocomplete="off">
  <input type="text" name="save_post_value" value="<?php echo $userPosts.", ".$postid;  ?>"> 
  <button  type="submit" class="save_post btn btn-danger">Update</button>
</form>

How can I check if a value is already in the input and if so, don't echo it?

A way would be to have them in an Array and then output in the input field the unique array, not sure if there is a shorter way.

Trying:

$allPosts = array($userPosts.", ".$postid); 
$allPosts = array_unique($allPosts); 

<input type="text" name="save_post_value" value="<?php foreach ($allPosts as $value) { echo $value; } ?>">

Also:

$allPosts = array($userPosts.", ".$postid); 
$allPosts = array_unique($allPosts); 
$allPosts = explode(", ", $allPosts);
<input type="text" name="save_post_value" value="<?php echo $allPosts; ?>"

And tried with implode() too:

$allPosts = array($userPosts.", ".$postid); 
$allPosts = array_unique($allPosts); 
$allPosts = implode(", ", $allPosts);
<input type="text" name="save_post_value" value="<?php echo $allPosts; ?>"

Answer 1

This is very basic example, but I think that this can be useful for your needs:

<?php
// Input data
$userPosts = '19000, 23138, 23138';
$postid = '23138';

// With array
$userPosts = str_replace(' ', '', $userPosts);
if (empty($userPosts)) {
    $a = array();
} else {
    $a = explode(',', $userPosts);
}   
$a = array_unique($a, SORT_STRING);
if (in_array($postid, $a) === false) {
    $a[] = $postid;
}
$userPosts = implode(', ', $a);
echo 'Result using array: '.$userPosts.'</br>';
?> 

UPDATE:

It is possible to use a function. Check for empty posts is made using empty().

<?php
function getUniquePosts($xposts, $xid) {
    $xposts = str_replace(' ', '', $xposts);
    if (empty($xposts)) {
        $a = array();
    } else {
        $a = explode(',', $xposts);
    }   
    $a = array_unique($a, SORT_STRING);
    if (in_array($xid, $a) === false) {
        $a[] = $xid;
    }
    $xposts = implode(', ', $a);
    $xposts = ltrim($xposts, ",");

    return $xposts;
}

$userPosts = '19000, 23138, 23138';
$postId = '23138';
echo getUniquePosts($userPosts, $postId).'</br>';
?> 

Then when loading form you can try with this:

...
$a = array_unique($a, SORT_STRING); 
...
update_user_meta($user_id, 'save_post', getUniquePosts($a, $user_id));