Attempting to compare values in two arrays

Question

I have a list of users on a webpage and am trying to compare each username with a list of users in an array. But for some reason the following code always returns false. Some usernames do match and should therefore display a yes next to the username.

foreach($result AS $user){
    foreach($listarray AS $name){
        if($user['username'] == $name){
            $whitelisted = 'Yes';
        } else {
            $whitelisted = 'No';
        }
    }
    echo '<tr><td><p>'.$user['username'].'</p></td><td><p>'.$user['location'].'</p></td><td><p>'.$user['date_joined'].'</p></td><td><p>'.$whitelisted.'</p></td>';
}

Why is this comparison returning false even when some names should match?

Please post some sample data; hard to tell what's wrong without seeing your data structure. — elixenide
– elixenide, Commented Dec 6, 2013 at 18:51
Does $user['username'] exist? Do the cases match? Is there extra whitespace in either $user['username'] or $name? You'll probably need to post some actual data to get a good answer here :) — candu
– candu, Commented Dec 6, 2013 at 19:00

Khawer Zeshan · Accepted Answer · 2013-12-06 19:05:12Z

1

You need to break the inner foreach loop if there is a matching element. Alternatively you can use the in_array function to check if there is value exists in an array

foreach($result AS $user){
    $whitelisted = 'No';
    if (in_array($user['username'], $listarray ))
    {
       $whitelisted = 'Yes';
    }
    echo '<tr><td><p>'.$user['username'].'</p></td><td><p>'.$user['location'].'</p></td><td><p>'.$user['date_joined'].'</p></td><td><p>'.$whitelisted.'</p></td>';
}

edited Dec 6, 2013 at 19:05

answered Dec 6, 2013 at 18:59

Khawer Zeshan

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1 Comment

crmepham Over a year ago

More elegant thank you, I totally forgot the in_array function.

Ken · Accepted Answer · 2013-12-06 18:53:22Z

1

You need to exit the loop with a break command when you find the match. Right now, your code is looping through each value in $result, then it takes that value and compares it to every value in $listarray. It's not comparing side-by-side.

answered Dec 6, 2013 at 18:53

Ken

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Comments

Félix Adriyel Gagnon-Grenier · Accepted Answer · 2013-12-06 19:34:26Z

1

the result of the comparison is assigned to a simple variable, overwriting it each time. that way if the last one is false it will always be false. moreover, the second foreach will execute all its iteration before getting back to the first one. this can be fixed with continue;:

foreach($result AS $user){
  foreach($listarray AS $name){
    if($user['username'] == $name){
        $whitelisted = 'Yes';
        continue; // that way when conpared as true, your other foreach can display result
    } else {
        $whitelisted = 'No';
    }
}
echo '<tr><td><p>'.$user['username'].'</p></td><td><p>'.$user['location'].'</p></td><td><p>'.$user['date_joined'].'</p></td><td><p>'.$whitelisted.'</p></td>';
}

edited Dec 6, 2013 at 19:34

answered Dec 6, 2013 at 19:23

Félix Adriyel Gagnon-Grenier

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Comments

Eugen Rieck · Accepted Answer · 2013-12-06 18:56:57Z

0

foreach($result AS $user){
    $whitelisted = 'No';
    foreach($listarray AS $name){
        if($user['username'] == $name){
            $whitelisted = 'Yes';
        }
    }
    echo '<tr><td><p>'.$user['username'].'</p></td><td><p>'.$user['location'].'</p></td><td><p>'.$user['date_joined'].'</p></td><td><p>'.$whitelisted.'</p></td>';
}

answered Dec 6, 2013 at 18:56

Eugen Rieck

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3 Comments

Khawer Zeshan Over a year ago

You need to break the inner foreach if there is a matching element. Assume if first element is the match but last element is not a match then $whitelisted will always be NO

Eugen Rieck Over a year ago

Khawer, that is wrong: "No" will only be seen, if there is no hit - it is assigned before the inner loop

Khawer Zeshan Over a year ago

Sorry my bad got it now, But still breaking the inner loop will save some time as if there is a match then there is no need to compare any further.

sravis · Accepted Answer · 2013-12-06 19:06:06Z

0

$a = array('me', 'you', 'ours');
$b = array('me', 'mine', 'you');

$merge = array_merge($a, $b); // MERGER ARRAY
$dups = array_count_values($merge); // COUNT DUPLICATES

// STORE ALL DUPLICATED VALUES
$dup = array();
foreach($dups as $k => $v) {
    if($v > 1) {
        $dup[] = $k;
    }
}

echo '<pre> Duplicates: '; print_r($dup); echo '</pre>';

Result:

 Duplicates: Array
(
    [0] => me
    [1] => you
)

Check out my PHP Fiddle: http://phpfiddle.org/main/code/t71-4db

answered Dec 6, 2013 at 19:06

sravis

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