diff --git a/mod/scorm/report/graphs/graph.php b/mod/scorm/report/graphs/graph.php
index 3d9b7f44032..5e8ac0caabb 100644
--- a/mod/scorm/report/graphs/graph.php
+++ b/mod/scorm/report/graphs/graph.php
@@ -28,23 +28,23 @@ require_once($CFG->libdir . '/graphlib.php');
 require_once($CFG->dirroot.'/mod/scorm/report/reportlib.php');
 require_once($CFG->dirroot.'/mod/scorm/locallib.php');
 
-$scoid = required_param('scoid', PARAM_INT);// sco ID
+$scoid = required_param('scoid', PARAM_INT);// SCO ID.
 
-$sco = $DB->get_record('scorm_scoes', array('id'=>$scoid), '*', MUST_EXIST);
-$scorm = $DB->get_record('scorm', array('id'=>$sco->scorm), '*', MUST_EXIST);
+$sco = $DB->get_record('scorm_scoes', array('id' => $scoid), '*', MUST_EXIST);
+$scorm = $DB->get_record('scorm', array('id' => $sco->scorm), '*', MUST_EXIST);
 $cm = get_coursemodule_from_instance('scorm', $scorm->id, 0, false, MUST_EXIST);
-$course = $DB->get_record('course', array('id'=>$scorm->course), '*', MUST_EXIST);
+$course = $DB->get_record('course', array('id' => $scorm->course), '*', MUST_EXIST);
 
 
-// Capability Checks
+// Capability Checks.
 require_login($course, false, $cm);
 $contextmodule = context_module::instance($cm->id);
 require_capability('mod/scorm:viewreport', $contextmodule);
 
-// find out current groups mode
+// Find out current groups mode.
 $currentgroup = groups_get_activity_group($cm, true);
 
-// Group Check
+// Group Check.
 if (empty($currentgroup)) {
     // All users who can attempt scoes.
     $students = get_users_by_capability($contextmodule, 'mod/scorm:savetrack', 'u.id' , '', '', '', '', '', false);
@@ -95,13 +95,14 @@ if (!empty($allowedlist)) {
                 if (empty($range)) {
                     continue;
                 }
-                $percent = round((($score*100)/$range), 2);
-                if (empty($usergrades[$attempt->userid]) || !isset($usergrades[$attempt->userid]) || ($percent > $usergrades[$attempt->userid]) || ($usergrades[$attempt->userid] === '*')) {
+                $percent = round((($score * 100) / $range), 2);
+                if (empty($usergrades[$attempt->userid]) || !isset($usergrades[$attempt->userid])
+                        || ($percent > $usergrades[$attempt->userid]) || ($usergrades[$attempt->userid] === '*')) {
                     $usergrades[$attempt->userid] = $percent;
                 }
                 unset($percent);
             } else {
-                // User has made an attempt but either SCO was not able to record the score or something else is broken in SCO
+                // User has made an attempt but either SCO was not able to record the score or something else is broken in SCO.
                 if (!isset($usergrades[$attempt->userid])) {
                     $usergrades[$attempt->userid] = '*';
                 }
@@ -111,7 +112,7 @@ if (!empty($allowedlist)) {
 }
 
 $bandlabels[] = get_string('invaliddata', 'scormreport_graphs');
-for ($i = 1; $i <= $bands-1; $i++) {
+for ($i = 1; $i <= $bands - 1; $i++) {
     $bandlabels[] = ($i - 1) * $bandwidth . ' - ' . $i * $bandwidth;
 }
 // Recording all users  who attempted the SCO,but resulting data was invalid.
@@ -119,7 +120,7 @@ foreach ($usergrades as $userpercent) {
     if ($userpercent === '*') {
         $graphdata[0]++;
     } else {
-        $gradeband = floor($userpercent/10);
+        $gradeband = floor($userpercent / 10);
         if ($gradeband != ($bands - 1)) {
             $gradeband++;
         }
@@ -135,12 +136,12 @@ $line->parameter['y_label_angle'] = 90;
 $line->parameter['x_label_angle'] = 0;
 $line->parameter['x_axis_angle'] = 60;
 
-//following two lines seem to silence notice warnings from graphlib.php
+// Following two lines seem to silence notice warnings from graphlib.php.
 $line->y_tick_labels = null;
 $line->offset_relation = null;
 
 $line->parameter['bar_size'] = 1;
-// don't forget to increase spacing so that graph doesn't become one big block of colour
+// Don't forget to increase spacing so that graph doesn't become one big block of colour.
 $line->parameter['bar_spacing'] = 10;
 $line->x_data = $bandlabels;
 
@@ -155,11 +156,11 @@ $line->y_data['allusers'] = $graphdata;
 $line->y_order = array('allusers');
 
 $ymax = max($line->y_data['allusers']);
-$line->parameter['y_min_left'] = 0;  // start at 0
+$line->parameter['y_min_left'] = 0;  // Start at 0.
 $line->parameter['y_max_left'] = $ymax;
 $line->parameter['y_decimal_left'] = 0; // 2 decimal places for y axis.
 
-//pick a sensible number of gridlines depending on max value on graph.
+// Pick a sensible number of gridlines depending on max value on graph.
 $gridlines = $ymax;
 while ($gridlines >= 10) {
     if ($gridlines >= 50) {
@@ -168,7 +169,7 @@ while ($gridlines >= 10) {
         $gridlines /= 2;
     }
 }
-
-$line->parameter['y_axis_gridlines'] = $gridlines + 1;
+$gridlines = max(2, ($gridlines + 1)); // We need a minimum of two lines.
+$line->parameter['y_axis_gridlines'] = $gridlines;
 
 $line->draw();