PHP function to return array with repeated values

Three problems with your current function.

1. $name and $c are reversed in the foreach loop. The names will be the keys
2. The loop doesn't stop after it gets the top counts
3. The function doesn't return anything.

You can fix it like this:

After you count and sort with

$count = array_count_values($ballot);
arsort($count);

you can get the max value by taking the first value from the rsorted counts.

$max = reset($count);

Then as you iterate, when you reach a name with a count !== the max count, break out of the loop.

foreach($count as $name => $c) {
    if ($c !== $max) break;
    $arr[] = $name;
}

And don't forget to return the result.

return $arr;

Another possibility is to use some built-in PHP functions. I agree starting with array_count_values() seems like a good idea.

$count = array_count_values($ballot);

After that you can get the max count using max()

$max = max($count);

Filter the counts to return only items with the max count

$top = array_filter($count, function($n) use ($max) {
     return $n == $max;
});

// PHP 7.4 version
// $top = array_filter($count, fn($n) => $n == $max);

And return the keys from that array to get the names.

return array_keys($top);

This solution keeps track as it goes.

function writeIn($ballot) {
    $tally = []; // How many votes did each person get
    $choice = []; // List of names with max occurrences
    $max = 0;
    array_walk($ballot, function($item) use(&$choice, &$tally, &$max) {
        if ( ! array_key_exists($item, $tally) ) {
            // If we haven't seen this name, add it with a count of 1
            $tally[$item] = 1;
        } else {
            // We saw this name already so increment its count
            $tally[$item]++;
        }
        // Check to see if the current name has exceeded or reached max
        if ( $tally[$item] > $max ) {
            // This is a new max so replace the choice list with this name
            $choice = [$item];
            $max = $tally[$item];
        } elseif ( $tally[$item] == $max ) {
            // This name has reached the current max so add it to the list
            $choice[] = $item;
        }
    });
    // Now we have the list of names with the most occurrences.
    return $choice;
}

Don't Panic's answer is a good one. There is also an optional search parameter to array_keys() to pass a search parameter which is applicable to this problem. Once you have the results sorted by count, and you know the max count, you can use that parameter to only return keys(name)s that match the associated count value.

<?php

$ballot = ['Alex', 'Michael', 'Harry', 'Dave', 'Michael', 'Victor', 'Harry', 'Alex', 'Mary', 'Mary'];

function writeIn($ballot) {
    $count = array_count_values($ballot);

    arsort($count);
    $max = reset($count);

    return array_keys($count, $max);
}

var_dump( writeIn($ballot));

Returns:

array(4) {
  [0]=>
  string(4) "Alex"
  [1]=>
  string(7) "Michael"
  [2]=>
  string(5) "Harry"
  [3]=>
  string(4) "Mary"
}