Guard fopen() results with a false-check before fwrite/fprintf/fclose

On PHP 7.4, calling fwrite()/fprintf()/fclose() with a false handle
(a failed fopen(), e.g. from a bad path, missing directory, or
permissions issue) just emits a warning and no-ops. On PHP 8.0+, these
functions require a resource argument and throw an uncaught TypeError
instead, turning what used to be a silent degradation into a fatal
crash of the whole request.

This patch wraps every fopen()-then-write call site in the codebase
(18 files) with an `if ($handle !== false) { ... }` check, matching
the existing pattern used elsewhere in the codebase. Where the same
$fpvar handle is threaded through shared helper functions
(enter_ban_list/banlist/whitelist, duplicated across
remove_variables_processing.php, remove_variables_processing_default.php,
modify_structure_learning.php and tier_description_processing_gom.php),
the guard was added inside those functions too for consistency, even
though the call sites are currently dead/commented-out in three of the
four files — so the same landmine doesn't reappear if that code is
ever re-enabled.

Verified empirically against PHP 8.3.28: fopen() on an unwritable path
followed by fwrite() on the resulting `false` throws
  TypeError: fwrite(): Argument #1 ($stream) must be of type resource, false given
without the guard; with the guard, the call is skipped instead of
crashing. The normal (successful fopen) path was also re-run through
mat_structure.php's structure_change() and still produces identical
output to before the change.

Reviewed by: Frederick M Muriithi <fredmanglis@gmail.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/sourcecodes/test_set_predictions.php b/sourcecodes/test_set_predictions.php
index 076188b4..f1806575 100644
--- a/sourcecodes/test_set_predictions.php
+++ b/sourcecodes/test_set_predictions.php
@@ -189,7 +189,9 @@ if($searchID!="")
     {
       //      $fpdata = fopen("./data/".$keyval."ts_input.txt","w");
       $fpdata = fopen($dir.$keyval."ts_upload.txt","w");
-      fwrite($fpdata,$searchID);
+      if ($fpdata !== false) {
+        fwrite($fpdata,$searchID);
+      }
     }
   $command = './run_scripts/run_test_set '.$keyval;
   $output = shell_exec("$command > /dev/null 2 > /dev/null &");