anche a me da lo stesso errore solo che ho replicato database e sito su un PC prendendo il codice già funzionante da un altro.

Notice: Undefined offset: 3 in /opt/lampp/htdocs/progetto/index.php on line 52

Notice: Undefined offset: 4 in /opt/lampp/htdocs/progetto/index.php on line 52
sul Macbook di partenza usando Xampp non mi da problemi e non mi ha mai segnalato questo tipo di errori.
ho importanto il tutto su Linux Ubuntu sempre utilizzando come server locale Xampp e segnala quell' errore.
non ho proprio idea del perchè...

il mio codice è questo.
Codice PHP:
       <?php
                         
include_once('db_connect.php');
                        
$query_ar"SELECT artist, title FROM Record ORDER BY code DESC ";

                        
$result_armysql_query($query_ar)
                        or die(
"error ar");
                        
                        while (
$result_row_ar=mysql_fetch_row(($result_ar))){
                        
$ar_array[]=$result_row_ar[1]." - ".$result_row_ar[0];
                        
                        }
                        
                        for(
$index=0$index<5$index++){
                        echo 
"[*]".$ar_array[$index]."";
                        
                        }
                        
?>

Codice PHP:
<?php
                        
                        
                        
include_once('db_connect.php');
                        
$query_random="SELECT userName FROM User";
                        
$result_random=mysql_query($query_random);
                        if(!
$result_random){
                        echo 
'ERROR
'
;
                        die(
"Could not query the database 
"
.mysql_error());
                        
                        }
                        
                        while (
$result_row=mysql_fetch_row(($result_random))){
                        
                        
$artist_array[]=$result_row[0];
                        
                        }
                        
                        
shuffle($artist_array);
                        for(
$index=0$index<5$index++){
                        
                        echo 
"[*]".$artist_array[$index]."";
                        
                        }
                        
?>

Codice PHP:
<?php
                    
                        
                           
include_once('db_connect.php');
                        
$query_comment"SELECT commentText, commentDate FROM Comment ORDER BY code DESC ";

                        
$result_commentmysql_query($query_comment)
                        or die(
"error");
                        
                        while (
$result_row_comment=mysql_fetch_row(($result_comment))){
                        
$comment_array[]=$result_row_comment[1]." \"".substr($result_row_comment[0],0,150)."...\"";
                        
                        }
                        
                        for(
$index=0$index<5$index++){
                        echo 
"[*]".$comment_array[$index]."";
                        
                        }
                        
?>
Codice PHP:
<?php
                         
include_once('db_connect.php');
                        
$query_rm"SELECT Record.title, Record.artist, AVG(Voting.vote) FROM Record JOIN Voting ON Record.code=Voting.record WHERE MONTH(Voting.votingDate)=MONTH(CURDATE()) GROUP BY Record.title ORDER BY AVG(Voting.vote) DESC ";

                        
$result_rmmysql_query($query_rm)
                        or die(
"error rm");
                        
                        while (
$result_row_rm=mysql_fetch_row(($result_rm))){
                        
$rm_array[]=$result_row_rm[0]." - ".$result_row_rm[1]." - ".substr($result_row_rm[2],0,3);
                        
                        }
                        
                        for(
$index=0$index<5$index++){
                        echo 
"[*]".$rm_array[$index]."";
                        
                        }
                        
?>

Codice PHP:
<?php
                         
include_once('db_connect.php');
                        
$query_am"SELECT artist, title FROM Record ORDER BY rating DESC ";
                        
                        
$result_ammysql_query($query_am)
                        or die(
"error am");
                        
                        while (
$result_row_am=mysql_fetch_row(($result_am))){
                        
$am_array[]=$result_row_am[1]." - ".$result_row_am[0];
                        
                        }
                        
                        for(
$index=0$index<5$index++){
                        echo 
"[*]".$am_array[$index]."";
                        
                        }
                        
?>