diff --git a/certificates/index.php b/certificates/index.php
index 6c9c42309a..790c37650e 100755
--- a/certificates/index.php
+++ b/certificates/index.php
@@ -10,7 +10,7 @@ require_once '../main/inc/global.inc.php';
 $action = isset($_GET['action']) ? $_GET['action'] : null;
 $certificate = new Certificate($_GET['id']);
 
-CustomCertificatePlugin::redirectCheck($certificate, intval($_GET['id']));
+CustomCertificatePlugin::redirectCheck($certificate, $_GET['id']);
 
 switch ($action) {
     case 'export':
diff --git a/plugin/customcertificate/src/CustomCertificatePlugin.php b/plugin/customcertificate/src/CustomCertificatePlugin.php
index 8d3175f9aa..6f009842d4 100644
--- a/plugin/customcertificate/src/CustomCertificatePlugin.php
+++ b/plugin/customcertificate/src/CustomCertificatePlugin.php
@@ -15,16 +15,19 @@ class CustomCertificatePlugin extends Plugin
 
     // When creating a new course this settings are added to the course
     public $course_settings = [
-            [
-                    'name' => 'customcertificate_course_enable',
-                    'type' => 'checkbox',
-            ],
-            [
-                    'name' => 'use_certificate_default',
-                    'type' => 'checkbox',
-            ],
+        [
+            'name' => 'customcertificate_course_enable',
+            'type' => 'checkbox',
+        ],
+        [
+            'name' => 'use_certificate_default',
+            'type' => 'checkbox',
+        ],
     ];
 
+    /**
+     * Constructor.
+     */
     protected function __construct()
     {
         parent::__construct(
@@ -39,6 +42,10 @@ class CustomCertificatePlugin extends Plugin
     }
 
     /**
+     * Instance the plugin.
+     *
+     * @staticvar null $result
+     *
      * @return CustomCertificatePlugin
      */
     public static function create()
@@ -190,7 +197,7 @@ class CustomCertificatePlugin extends Plugin
     /**
      * Get certificate data.
      *
-     * @param Certificate $id The certificate
+     * @param int $id The certificate
      *
      * @return array
      */
diff --git a/plugin/customcertificate/src/index.php b/plugin/customcertificate/src/index.php
index 7db298f002..1b7d837493 100644
--- a/plugin/customcertificate/src/index.php
+++ b/plugin/customcertificate/src/index.php
@@ -125,9 +125,6 @@ if ($enable) {
                 }
 
                 // Image manager
-                $base = api_get_path(SYS_UPLOAD_PATH);
-                $pathCertificates = $base.'certificates';
-
                 $fieldList = [
                     'logo_left',
                     'logo_center',
@@ -146,8 +143,7 @@ if ($enable) {
                         checkInstanceImage(
                             $certificateId,
                             $infoCertificate[$field],
-                            $field,
-                            $pathCertificates
+                            $field
                         );
                     }
 
@@ -170,8 +166,6 @@ if ($enable) {
 
                 // Certificate Default
                 if (intval($formValues['use_default'] == 1)) {
-                    $base = api_get_path(SYS_UPLOAD_PATH);
-
                     $infoCertificateDefault = Database::select(
                         '*',
                         $table,
@@ -921,14 +915,25 @@ if ($enable) {
     api_not_allowed(true, $plugin->get_lang('ToolDisabled'));
 }
 
-function checkInstanceImage($certificateId, $imagePath, $field, $path)
+/**
+ * Delete the file if there is only one instance.
+ *
+ * @param int    $certificateId
+ * @param string $imagePath
+ * @param string $field
+ * @param string $type
+ */
+function checkInstanceImage($certificateId, $imagePath, $field, $type = 'certificates')
 {
     $table = Database::get_main_table(CustomCertificatePlugin::TABLE_CUSTOMCERTIFICATE);
+    $imagePath = Database::escape_string($imagePath);
+
     $sql = "SELECT * FROM $table WHERE $field = '$imagePath'";
     $res = Database::query($sql);
     if (Database::num_rows($res) == 1) {
-        @unlink($path.$imagePath);
+        api_remove_uploaded_file($type, $imagePath);
     }
+
     $sql = "UPDATE $table SET $field = '' WHERE id = $certificateId";
     Database::query($sql);
 }