PHP script doesn't end - php

Question

So I got my script doing this:
I got a list of filenames (images), I loop through the array and load the images from Amazon S3 to my local storage. We are talking about 35k pictures which takes more than 3 hours.
After I downloaded all the images I want to make a redirect via header Location. But the script won't execute that. It's like it's stopping after the loop.
When I have a very small list of images to load it will work with no issues.
The apache error log doesn't show any errors. There is no php process running on the server after that. But the request is still running in the browser.
Ini settings are as followed:
ini_set( 'max_execution_time', 60 * 30 );
ini_set( 'memory_limit', '4096M' );
Foreach loop lookes like this:
foreach( $arrImages as $file ) {
$strPath = $strBasePath . DIRECTORY_SEPARATOR . $file['name'];
// check directory
$pos = strrpos( $strPath, DIRECTORY_SEPARATOR );
$dir = substr( $strPath, 0, $pos );
if( !is_dir( $dir ) ) {
exec( "mkdir -p " . $dir );
exec( "chmod -R 777 " . $strBasePath . DIRECTORY_SEPARATOR );
}
// check if file or path
if( !is_dir( $strPath ) ) {
// build filename
$lastSeparatorPos = strrpos( $strPath, DIRECTORY_SEPARATOR );
$filename = explode( '.', substr( $strPath, $lastSeparatorPos + 1, strlen( $strPath ) - 1 ) );
$clearedFilename = explode( '_', $filename[0] );
if( !in_array( $clearedFilename[0], $arrOrdernumbers ) && strpos( $dir, 'groups' ) == false && strpos( $dir, 'background' ) == false ) {
$intCountNotImported++;
}
else {
$handle = fopen( $strPath, 'wb' );
if( $handle == false ) {
\ImportLogger::log( $strPath . ' - Bild konnte nicht uebertragen werden' );
}
else {
// get File/Folder
$objImage = \S3::getObject( C_S3_BUCKET, $file['name'] );
fwrite( $handle, $objImage->body );
$intAmount++;
// Log every 100 Files
if( $intAmount % 100 == 0 ) {
\ImportLogger::log( $intAmount . ' Bilder uebertragen' );
}
}
fclose( $strPath );
}
}
}
\Debugger::sendEmail( 'xx#xxxx.de', 'Fetchimages', $intAmount . ' - Images loaded' ); // This E-Mail I still get
// Redirect is not happening
$strUrl = '/string/configurator2/compressimages';
header( 'Location: ' . $strUrl );
exit;
Any ideas what could cause this?
Thanks for your help!