Case Insensitive file_exists for large list of files - php

Question

I have a server folder with a large number of files, randomly named with a guid value (example file: c3c1a48e-a798-41bd-bd70-66ffdc619963.jpg ).
I need to do a case-insensitive search of that folder, as there might be an uppercase (or mixed case) version of the same filename. (I cannot convert existing files to all lowercase file names.)
The answers in this question
PHP Case Insensitive Version of file_exists() provide a function (shown below) that will 'glob' the entire folder into an array, then does a foreach search each item in the array.
This would seem to be a bit slow/inefficient, especially when searching a folder with many (thousands) of files.
Is there a more efficient way to do a case-insensitive filename search? Or is the use of the foreach loop - as shown in the below code - 'efficient enough'?
(This is the code recommended by the above question)
function fileExists($fileName, $caseSensitive = true) {
if(file_exists($fileName)) {
return $fileName;
}
if($caseSensitive) return false;
// Handle case insensitive requests
$directoryName = dirname($fileName);
$fileArray = glob($directoryName . '/*', GLOB_NOSORT);
$fileNameLowerCase = strtolower($fileName);
foreach($fileArray as $file) {
if(strtolower($file) == $fileNameLowerCase) {
return $file;
}
}
return false;
}

Answer 1

I cannot comment, though this can be an answer to your question: No. As of right now in your current state, it looks like you have to use that logic. -However- you could create logic to take those files that have capital letters and use copy($filename,strtolower($filename)) in the folder to make them lower case and then remove the old filenames that have capital letters. . Then in the future upon adding more files to the many, strtolower($new_file_name) before adding the file to the system. I agree with you though that that logic does seem slow, especially with thousands of files.
It contradicts you saying you cannot rename /convert the file names, though once you do it, that will be the only time you would have to rename them.