Unique random character generator

Question

PHP beginner here. Will the following code do what I've noted correctly?

//Random code generator
function random_string_func() {
    //Hash generator
    $generated_hash = md5(uniqid(rand()));

    //get all existing hashes and store them into an array
    $existing_hashes = FrmEntryMeta::get_entry_metas_for_field(198, '', '', array()); //change 198 to the ID of the date field

    //Check if the newly generated hash exists in WP database
    if(in_array($generated_hash, $existing_hashes)){ 
        //If yes, generate a new hash
        $generated_hash = md5(uniqid(rand()));
    }
    return $generated_hash;
}
add_shortcode( 'random_string', 'random_string_func' );