PHP Notice: Undefined offset: 0 fixable? - php

Question

I have a "get first image script" I am using that is all over the internet but am getting the error:
PHP Notice: Undefined offset: 0
the script is:
function get_first_image() {
global $post, $posts;
$first_img = '';
ob_start();
ob_end_clean();
$output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i',$post->post_content, $matches);
$first_img = $matches [1] [0];
return $first_img;
}
can this be fixed?

Answer 1

Based on your regex this could happen if the <img> tag has no src attribute or if there are no <img> tags at all.
As others have suggested you could fix this by checking $matches first, but I'd like to suggest an alternate approach that may be more robust for parsing html in php, since using regex to do this is discouraged.
function get_first_image() {
global $post;
$first_img = '';
$dom = new DOMDocument();
$dom->loadHtml($post->post_content);
foreach ($dom->getElementsByTagName('img') as $img) {
if ($img->hasAttribute('src')) {
$first_image = $img->getAttribute('src');
break;
}
}
return $first_img;
}
The above function uses php's DOMDocument Class to iterate over <img> tags and get the src attribute if it exists. (Note: I removed the ob_start() and ob_end_clean() functions from your code because I don't understand what purpose they were serving)

Answer 2

You can do this:
$first_img = isset($matches[1][0]) ? $matches[1][0] : false;
Which will, then, return false if the first position in this two dimension array would not exist.

Answer 3

Before operator:
$first_img = $matches [1] [0];
insert the line:
var_dump($matches);
Make sure, that $matches is an array, and has two dimensions.