added url input in upload form closes #69

inc/core.php

@@ -518,4 +518,18 @@ function endswith($string, $test) {
     $testlen = strlen($test);
     if ($testlen > $strlen) return false;
     return substr_compare($string, $test, $strlen - $testlen, $testlen) === 0;
+}
+
+function remote_filesize($url) {
+    static $regex = '/^Content-Length: *+\K\d++$/im';
+    if (!$fp = @fopen($url, 'rb')) {
+        return false;
+    }
+    if (
+        isset($http_response_header) &&
+        preg_match($regex, implode("\n", $http_response_header), $matches)
+    ) {
+        return (int)$matches[0];
+    }
+    return strlen(stream_get_contents($fp));
 }