diff --git a/helpers/helpers.php b/helpers/helpers.php
index bf704b1..d72ca82 100644
--- a/helpers/helpers.php
+++ b/helpers/helpers.php
@@ -39,7 +39,7 @@ function is_php($version)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      */
     function escapeHtml($string)
     {
@@ -56,7 +56,7 @@ function escapeHtml($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 09/21/2021 00:05
@@ -79,7 +79,7 @@ function htmlEscape($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      */
     function escapeHtmlAttr($string)
     {
@@ -96,7 +96,7 @@ function escapeHtmlAttr($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 09/23/2021 44:34
@@ -119,7 +119,7 @@ function escapeHtmlAttribute($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      */
     function escapeJs($string)
     {
@@ -172,7 +172,7 @@ function escape_input_var($var)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 09/20/2021 58:14
@@ -195,7 +195,7 @@ function escapeCss($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      */
     function escapeUrl($string)
     {
@@ -229,13 +229,17 @@ function removeInvisibleCharacters($str, $urlEncoded = true)
      *
      * @param $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 05/25/2021 58:03
      */
     function escape_html($string)
     {
+        if ($string === null) {
+            return null;
+        }
+
         return (new Escape())->escapeHtml($string);
     }
 }
@@ -245,13 +249,17 @@ function escape_html($string)
      *
      * @param $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 05/25/2021 58:41
      */
     function escape_html_attribute($string)
     {
+        if ($string === null) {
+            return null;
+        }
+
         return (new Escape())->escapeHtmlAttribute($string);
     }
 }
@@ -261,13 +269,17 @@ function escape_html_attribute($string)
      *
      * @param $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 05/25/2021 59:04
      */
     function escape_js($string)
     {
+        if ($string === null) {
+            return null;
+        }
+
         return (new Escape())->escapeJs($string);
     }
 }
@@ -277,13 +289,17 @@ function escape_js($string)
      *
      * @param $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 05/25/2021 59:24
      */
     function escape_css($string)
     {
+        if ($string === null) {
+            return null;
+        }
+
         return (new Escape())->escapeCss($string);
     }
 }
@@ -293,13 +309,17 @@ function escape_css($string)
      *
      * @param $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 05/25/2021 59:40
      */
     function escape_url($string)
     {
+        if ($string === null) {
+            return null;
+        }
+
         return (new Escape())->escapeUrl($string);
     }
 }
diff --git a/src/Escape.php b/src/Escape.php
index 2e2f443..88ad497 100644
--- a/src/Escape.php
+++ b/src/Escape.php
@@ -22,7 +22,7 @@
  */
 class Escape
 {
-    const VERSION = '1.0.9';
+    const VERSION = '1.1.0';
 
     /**
      * Character set
@@ -374,7 +374,7 @@ public function sanitizeFilename($str, $relative_path = false)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      */
     public function escapeHtml($string)
     {
@@ -391,7 +391,7 @@ public function escapeHtml($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 09/21/2021 00:05
@@ -413,7 +413,7 @@ public function htmlEscape($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      */
     public function escapeHtmlAttribute($string)
     {
@@ -433,7 +433,7 @@ public function escapeHtmlAttribute($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      */
     public function escapeJs($string)
     {
@@ -450,7 +450,7 @@ public function escapeJs($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      * @author   : 713uk13m <dev@nguyenanhung.com>
      * @copyright: 713uk13m <dev@nguyenanhung.com>
      * @time     : 09/20/2021 58:14
@@ -473,7 +473,7 @@ public function escapeCss($string)
      *
      * @param mixed $string
      *
-     * @return string
+     * @return string|null
      */
     public function escapeUrl($string)
     {
@@ -533,15 +533,15 @@ public function escapeInput($var)
         if (is_string($var)) {
             if ($this->isJson($var)) {
                 return $var;
-            } else {
-                $var = trim($var);
-                $var = $this->xssClean($var);
-                $var = strip_tags($var);
-                $var = $this->escapeHtml($var);
-                $var = htmlspecialchars($var, ENT_QUOTES | ENT_HTML5 | ENT_XHTML, 'UTF-8');
-
-                return trim($var);
             }
+
+            $var = trim($var);
+            $var = $this->xssClean($var);
+            $var = strip_tags($var);
+            $var = $this->escapeHtml($var);
+            $var = htmlspecialchars($var, ENT_QUOTES | ENT_HTML5 | ENT_XHTML, 'UTF-8');
+
+            return trim($var);
         }
 
         return $var;