Catch and handle smarty fetch file not found

Question

I have some smarty template code like the below:

{fetch file="https://example.com/file.php" assign='value'}

However, if the URL can't be reached, it 500 error's the page. Error logs reveal "{fetch} cannot read resource".

How would I catch the above to avoid it crashing the page if the URL is unavailable? e.g. if it was a var I could check it with isset to see if it is set but since its a url I don't know how to say "if not found, do this".

Tried the below but no luck.

{if file_exists('https://example.com/file.php')} 
{fetch file="https://example.com/file.php" assign='value'}
{/if}

Answer 1

Need to use smarty function (move this function to smarty function directory):

function smarty_function_checkurl($params)
{
    if (isset($params['url'])) {

        $url      = $params['url'];
        $parsed   = parse_url($url);
        $domain   = str_replace('www.', '', $parsed['host']);
        $response = checkdnsrr($domain);

        if ($response) {

            $file_headers = @get_headers($url);

            if ($file_headers && strpos($file_headers[0], ' 200 OK') !== false) {
                return true;
            }
        }

    }

    return false;
}

and then in .tpl file:

{if {checkurl url="https://example.com/file.php"}}
    YES
    {fetch file="https://example.com/file.php" assign='value'}
{else}
    NOT
{/if}