added has_php helper.

laravel/helpers.php

@@ -373,4 +373,15 @@ function value($value)
 function with($object)
 {
 	return $object;
+}
+
+/**
+ * Determine if the current version of PHP is at least the supplied version.
+ *
+ * @param  string  $version
+ * @return bool
+ */
+function has_php($version)
+{
+	return version_compare(PHP_VERSION, $version) >= 0;
 }