I made this function named "array_getMax" that returns te maximum value and index, from array:
<?php
function array_search_all($needle, $haystack)
{foreach ($haystack as $k=>$v) {
   
        if($haystack[$k]==$needle){
       
           $array[] = $k;
        }
    }
    return ($array);
   
}
function array_getMax($array){
        
    $conteo=array_count_values($array);
    
    if( count($conteo)==1 ){return  $array;       
    }
       
    arsort($array);
    
    $maxValue=null;
    $keyValue=null;
    foreach($array as $key=>$value){
        if($maxValue==null){
            $maxValue=$value;
            $keyValue=$key;
            break;
        }        
    }
    
    $resultSearch=array_search_all($maxValue, $array);
        
   return  array_fill_keys($resultSearch, $maxValue);
    
    
}
$arreglo=array('e1'=>99,'e2'=>'99','e3'=>1,'e4'=>1,'e5'=>98);
    
    var_dump(array_getMax($arreglo));
?>
I hope some one find this usefull