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, 15 insertions, 7 deletions

diff --git a/sourcecodes/modify_structure_learning.php b/sourcecodes/modify_structure_learning.php
index 1b0a70ef..c4e66bf0 100644
--- a/sourcecodes/modify_structure_learning.php
+++ b/sourcecodes/modify_structure_learning.php
@@ -11,8 +11,10 @@ $dir="/tmp/bnw/";
 $tf=$dir.$keyval."del_var.txt";
 $fpvar = fopen("$tf","w");
 
-fwrite($fpvar,"$tier");
-fclose($fpvar);
+if ($fpvar !== false) {
+  fwrite($fpvar,"$tier");
+  fclose($fpvar);
+}
 }
 
 
@@ -28,9 +30,11 @@ function enter_ban_list($t1,$s1,$t2,$s2,$tier_d,$fpvar)
             $data_val_2=$tier_d[$t2][$j];
             if($data_val_1!=$data_val_2)
             {
-               
-               fprintf($fpvar,"%s\t%s\n",$data_val_1,$data_val_2); 
-              
+
+               if ($fpvar !== false) {
+                 fprintf($fpvar,"%s\t%s\n",$data_val_1,$data_val_2);
+               }
+
 
             }
    
@@ -151,7 +155,9 @@ for ($i=0;$i<$n;$i+=2)
 
 	if($d1!="" && $d2!="")
 	{
-  		fprintf($fpvar,"%s\t%s\n",$d1,$d2);
+  		if ($fpvar !== false) {
+  		  fprintf($fpvar,"%s\t%s\n",$d1,$d2);
+  		}
   		$nn++;
 	}
 
@@ -177,7 +183,9 @@ $d2=trim($data[$ii]);
 
 if($d1!="" && $d2!="")
 {
-  fprintf($fpvar,"%s\t%s\n",$d1,$d2);
+  if ($fpvar !== false) {
+    fprintf($fpvar,"%s\t%s\n",$d1,$d2);
+  }
   $nn++;
 }