Feda /dev/

public function checkValidPassword( $password ){
    if( is_null($password) || empty($password) ) return false;

$pwd_split = str_split( $password );

//start R4
$array_differents = array();
foreach ($pwd_split as $key => $char) {
    if( !in_array($char, $array_differents) ){
        array_push($array_differents, $char);
    }
}
if( count($array_differents) < 5 ){
    return false; //R4: 5 differents characters minimum
}
//end R4

//start R5
foreach ($pwd_split as $key => $char) {

    $aux_ascii_value   = ord($char); //actual ascii value for this char

    if( isset($pwd_split[$key+1]) &&
        isset($pwd_split[$key+2]) &&
        isset($pwd_split[$key+3]) ) {
        $next_first_value  = ord($pwd_split[$key+1]);
        $next_second_value = ord($pwd_split[$key+2]);
        $next_third_value  = ord($pwd_split[$key+3]);

        if( abs($aux_ascii_value - $next_first_value) == 1 &&
            abs($aux_ascii_value - $next_second_value) == 2 &&
            abs($aux_ascii_value - $next_third_value) == 3 ){
            return false;
        }
    }
}
//end R5

//start R1, R2, R3
if( preg_match( '/[a-z][^a-z]*[a-z]/i', $password ) //R2: two letters
    && preg_match( '~\d.*\d~', $password )          //R3: two numbers
    && strlen( $password ) >= 8 ){                  //R1: minimum eight digits
    return true;
}
else {
    return false;
}
//end R1, R2, R3

return false;
}