array_flip to print duplicate values in comma separated format

Question

I\'m trying to use array_flip to print duplicate values in a comma separated format

$a=array(\"a\"=>\"red\",\"b\"=>\"green\",\"c\"=>\"b         


        

Answer 1

array_flip will not give your expected output. Instead of this you can write your custom function like:

$a=array("a"=>"red","b"=>"green","c"=>"blue","d"=>"blue");
$flip = array_flip_custom($a);

print_r($flip);
function array_flip_custom($a){
    $flip = array();
    foreach($a as $index=>$key){
        if($flip[$key]){
            $flip[$key] .= ','.$index;
        } else {
            $flip[$key] = $index;
        }
    }
    return $flip;
}

Will give output:

Array ( [red] => a [green] => b [blue] => c,d )