PHP check file extension [duplicate]

pathinfo is what you're looking for

PHP.net

$file_parts = pathinfo($filename);

switch($file_parts['extension'])
{
    case "jpg":
    break;

    case "exe":
    break;

    case "": // Handle file extension for files ending in '.'
    case NULL: // Handle no file extension
    break;
}

$info = pathinfo($pathtofile);
if ($info["extension"] == "jpg") { .... }