Translating status codes to messages in log files

What you have looks problematic in a few ways.

• You have a poor data structure for your localization strings. You have these in an array the must be iterated every single time you are doing a lookup against it. This is an linear complexity (O(n)) operation that when executed inside your loop (another O(n) iteration) give you O(n^2) overall performance. @TimSparrow has touched on a good alternative - to load the localization strings into an associative array the will allow O(1) lookup when being used - but perhaps didn't explain how critical this is to your performance. By building such a data structure up front, you whole algorithm goes to O(m) (to build localization data structure) + O(n) (from your log file loop) instead of O(m * n). To illustrate the impact to your performance, let assume you have a 10K line log file and a 100 line localization file. With your current code, this means you could have up to 1 Million lookup operations you have to perform vs. 10,100 if using a proper data structure.
• This code is a memory hog. You store every file you are working with wholly in memory, as well as storing the same data in duplicate in the result arrays you are building, not to mention all the temporary array/string conversion you have that, again mean you are going to be holding that information in duplicate in memory. If you can get the memory utilization more optimized here, then you may be more able to do things like for each of the individual log into their own process to parallelize the work.
• You should consider working with the rows in a more structured manner vs. working with them primarily as strings. fgetcsv(), fputcsv() or similar give you better ways to parse through and write your files.

Incorporating the above thoughts should allow you to greatly streamline both the performance of your script as well as just simplify how it works. You might end up with something like:

$localizations = [];
$handle = fopen('ErrCODES/data_en.properties','r');
// read lines from file one at a time.
while ($line = fgetcsv($handle, 0, ' ')) {
    // this part may vary based on your format
    $localizations[$line[0]] = $line[1];
}
fclose($handle);

$logFiles = glob($uploadDIR.$filepath."/original/*.[lL][oO][gG]");
// here is where at some point you may want to fork processes to paralellize
// now it is serial foreach loop
foreach ($logFiles as $logFile) {
    $translatedFile = str_replace('/original', '/translation/', $logFile); 
    $logHandle = fopen($logFile,'r');
    $translateHandle = fopen($translatedFile, 'w+');
    while($line = fgetcsv($logHandle, 0, ' ') {
        // apply localization
        if(!empty($line[4]) && isset($localization[$line[4]])) {
            $line[4] = $localization[$line[4]];
        }
        fputcsv($translateHandle, $line, ' ');
    }
    fclose($translateHandle);
    fclose($logHandle);
}

A few final thoughts on style: - Your style is a little bit all over the place, which makes your code a littel hard to read. - Particularly variable naming is odd. PHP tends to use a mix of camelCase and snake_case in most code bases you will find (internal PHP functions mix both unfortunately). Your approach to variable syntax is very haphazard, sometimes oddly putting portions of variable names in upper case with apparent cohesive approach, sometimes first letter is uppercase, sometimes it is lower case, etc. - Your indentations are inconsistent. - You could be well-served by better use of spacing around flow control operators. A line of code like if(isset($LINEarray[0])){$newline .= $LINEarray[0]." ";} is extremely hard to read. - Consider familiarizing yourself with the PHP-FIG PHP standards, particularly PSR-1 and PSR-2 which deal with aspects of coding style. These are pretty much the de-facto industry standards.