Call to undefined function is_numerric()

On Apache's error log:
PHP Fatal error: Call to undefined function is_numerric() in xxxxx sites/all/modules/user_import/supported/user.inc on line 86

$ diff -u user.inc user.new.inc
--- user.inc 2013-08-12 01:29:11.000000000 +0300
+++ user.new.inc 2013-08-25 15:02:21.000000000 +0300
@@ -83,7 +83,7 @@
$parsed['year']
);

- if (!empty($timestamp) && is_numerric($timestamp)) {
+ if (!empty($timestamp) && is_numeric($timestamp)) {
$value = $timestamp;
}
}

### patch attached.