PHP checking if file exists on webp image not working - php

Question

So i'm trying to check if there is a webp image format on the url retrieved from get_the_post_thumbnail_url()
This is not working how I would expect though.
Here is the code im working with:
if (!file_exists($thePostThumbUrl))
$thePostThumbUrl = str_replace("_result.webp", "." . $ext, $thePostThumbUrl);
if I echo the thumb url it gets the correct image with a .webp format
echo $thePostThumbUrl . '<br/ >';
Displays:
image url + _result.webp
I know the version of PHP im working with is PHP/5.6.30

Answer 1

Ok so as Akintunde suggested, the file_exists function wont work with the url of the image. So the code needed to be modified to use the server path instead.
This code does the trick:
$ext = pathinfo($thePostThumbUrl, PATHINFO_EXTENSION);
$thePostThumbPath = str_replace("http://localhost", "", $thePostThumbUrl);
if (!file_exists($_SERVER['DOCUMENT_ROOT'] . $thePostThumbPath)) {
$thePostThumbUrl = str_replace("_result.webp", "." . $ext, $thePostThumbUrl);
}
Thansk Akintunde for pointing me in the right direction :)

Answer 2

I wrote a function that checks whether a given image exists in webp format on the server:
function webpExists($img_src){
$env = array("YOUR_LOCAL_ENV", "YOUR_STAGING_ENV", "YOUR_PROD_ENV");
$img_src_webp = str_replace(array(".jpeg", ".png", ".jpg"), ".webp", $img_src);
$img_path = str_replace($env, "", $img_src_webp);
return file_exists($_SERVER['DOCUMENT_ROOT'] . $img_path);
}

Answer 3

You need to use CURL for this case because it's a URL.
Example:
function checkRemoteFile($url)
{
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
// don't download content
curl_setopt($ch, CURLOPT_NOBODY, 1);
curl_setopt($ch, CURLOPT_FAILONERROR, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
if(curl_exec($ch)!==FALSE)
{
return true;
}
else
{
return false;
}
}