cover fflush function (#1583)

Author: Shamzik

tests/phpt/dl/473_file_for_k2.php

@@ -0,0 +1,33 @@
+@ok
+<?php
+  var_dump (basename ('..'));
+  var_dump (basename ('phpt/'));
+  var_dump (basename ('phpt'));
+  var_dump (basename ('abacaba'));
+  var_dump (basename ('.'));
+  var_dump (basename ('/etc/sudoers.d', '.d'));
+
+  $filename = '/tmp/' . rand(1, 2e9);
+  var_dump (is_file ($filename));
+//  var_dump ($filename);
+  $file = fopen ($filename, "w");
+  fwrite ($file, "1232225\n");
+  if (fwrite ($file, "qwreqer") != 7) {
+    echo "error1\n";
+  }
+  if (fwrite ($file, "") !== 0) {
+    echo "error2\n";
+  }
+  if (@(fwrite ("asdasdasd", "") !== false)) {
+    echo "error3\n";
+  }
+  fflush ($file);
+  fwrite ($file, "asdfdaf\n");
+  fwrite ($file, "asdfdaf");
+  fflush ($file);
+//  var_dump (fread ($file, 100));
+  fclose ($file);
+  if (@(fwrite ($file, "1231") !== false)) {
+    echo "error4\n";
+  }
+