注意:未定义的偏移量:3 行

我是一个PHP新手，我收到了两个关于作为图库一部分的代码的通知，你能帮我弄清楚吗？通知是

注意：未定义的偏移量：3 in/home/raj/public_html/viewgallery.php 在第 408
行 注意：未定义的偏移量：3 in/home/raj/public_html/viewgallery.php 在第 426 行

408路是

    'pcaption' => $caption_array[$next]);

而 426 行是

$result_final.= '<div class="limage"><table><tr><td><table class="image"><tr><td><a href="photos/'.$cname.'/'.$caption_array[$next].'/'.$q.'/"><img src="' . $images_dir . '/' . $photo_filename . '"  alt=" ' . $photo_keywords . '"></a><div class="caption">' . $photo_caption . '</div><div class="excerpt">' . $photo_description . '</div></td></tr></table></td></tr></table><div class="underline"></div></div>'.$backString.'</div>';

上面的行是此代码的一部分...

$next = 0;
$prev = 0;
if ($ct > 1)
{

$key = array_search($pcaption, $caption_array);
$prev = $key - 1;
if ($prev < 0) $prev = $ct - 1;
$next = $key + 1;
$searchNext = $key + 1;

if ($next == $ct) $next = 0;
$total_count = count($caption_array);
$result_final.= "<div id='prevnext'>";
$parameters_next = array(
'cname' => $cname,
'pcaption' => $caption_array[$next]
);
$parameters_prev = array(
'cname' => $cname,
'pcaption' => $caption_array[$prev]
);

$categoryNamePrev = $cname;
$photoCaptionNext = $caption_array[$next];
$photoCaptionPrev = $caption_array[$prev];

if($q !='' && $searchNext==$ct ) {
    $previousUrl = 'photos/'.$categoryNamePrev.'/'.$photoCaptionPrev.'/'.$q.'/';
    $nextUrl = '/searchmyway.php?q='.$q.'&form_id%3Asearch=1';
} else {
    if($q != '') {
        $previousUrl = 'photos/'.$categoryNamePrev.'/'.$photoCaptionPrev.'/'.$q.'/';
        $nextUrl = 'photos/'.$categoryNamePrev.'/'.$photoCaptionNext.'/'.$q.'/';
    } else {
        $previousUrl = 'photos/'.$categoryNamePrev.'/'.$photoCaptionPrev.'/';
        $nextUrl = 'photos/'.$categoryNamePrev.'/'.$photoCaptionNext.'/';
    }   
}

$result_final.= '<span class="prev"><a href="'.$previousUrl.'"><img src="/photos/assets/left.png" alt="left navigation"></a></span>';
$result_final.= '<span class="next"><a href="'.$nextUrl.'"><img src="/photos/assets/right.png" alt="right navigation"></a></span>';
$result_final.= "</div>";
}
}
$key = array_search($pcaption, $caption_array);
$prev = $key - 1;
if ($prev < 0) $prev = $ct - 1;
$next = $key + 1;
$searchNext = $key + 1;
$parameters_next = array(
'cname' => $cname,
'pcaption' => $caption_array[$next]
);
$parameters_prev = array(
'cname' => $cname,
'pcaption' => $caption_array[$prev]
);
if($q != '') {
        $backString = '<a href="/searchmyway.php?q='.$q.'&form_id%3Asearch=1">Back</a>';
} else {
$backString  = '';
}

if($q == '') {
$result_final.= '<div class="limage"><table><tr><td><table class="image"><tr><td><a href="photos/'.$cname.'/'.$caption_array[$next].'/"><img src="' . $images_dir . '/' . $photo_filename . '"  alt=" ' . $photo_keywords . '"></a><div class="caption">' . $photo_caption . '</div><div class="excerpt">' . $photo_description . '</div></td></tr></table></td></tr></table><div class="underline"></div></div>'.$backString.'</div>';
} else  {
$result_final.= '<div class="limage"><table><tr><td><table class="image"><tr><td><a href="photos/'.$cname.'/'.$caption_array[$next].'/'.$q.'/"><img src="' . $images_dir . '/' . $photo_filename . '"  alt=" ' . $photo_keywords . '"></a><div class="caption">' . $photo_caption . '</div><div class="excerpt">' . $photo_description . '</div></td></tr></table></td></tr></table><div class="underline"></div></div>'.$backString.'</div>';
}