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, 21 insertions, 13 deletions

diff --git a/sourcecodes/execute_bn_gom.php b/sourcecodes/execute_bn_gom.php
index 8a728a24..93d46309 100644
--- a/sourcecodes/execute_bn_gom.php
+++ b/sourcecodes/execute_bn_gom.php
@@ -48,15 +48,19 @@ $n=count($dataname);
 
 $initialstring="digraph G {\n"."size=\"6,8\";  ratio = fill;\n"."node [shape=square,width=1.5];\n";
 $endstring="}";
-fwrite($fout,"$initialstring");
+if ($fout !== false) {
+  fwrite($fout,"$initialstring");
+}
 
 $g_file_name=$dir.$keyval."grviz_name_file.txt";
 $grviz_name_file=fopen($g_file_name,"w");
 
-for($i=0;$i<$n;$i++)
-{
-      $row_name=trim($dataname[$i]);  
-      fwrite($grviz_name_file,"$row_name\n");
+if ($grviz_name_file !== false) {
+  for($i=0;$i<$n;$i++)
+  {
+        $row_name=trim($dataname[$i]);
+        fwrite($grviz_name_file,"$row_name\n");
+  }
 }
 
 for($i=1;$i<=$n;$i++)
@@ -71,18 +75,22 @@ for($i=1;$i<=$n;$i++)
 	   {
                $col_val=trim($col_arr[$j]);
                if($col_val==1)
-               { 
+               {
                   $col_name=trim($dataname[$j]);
-                  fprintf($fout,"%s -> %s;\n",$ii,$j);  
+                  if ($fout !== false) {
+                    fprintf($fout,"%s -> %s;\n",$ii,$j);
+                  }
                   //fprintf($fouttemp,"%s -> %s;\n",$row_name,$col_name);
-                 
+
 	        }
           }
-          
-     
-} 
-fwrite($fout,"$endstring");   
-fclose($fout);
+
+
+}
+if ($fout !== false) {
+  fwrite($fout,"$endstring");
+  fclose($fout);
+}
 
 
 shell_exec('./run_scripts/run_octave '.$keyval);