diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0b4e4b651..5ac9ab572 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
     * Fixed fatal error with some markdown links [getgrav/grav-premium-issues#95](https://github.com/getgrav/grav-premium-issues/issues/95)
     * Fixed markdown media operations not working when using `image://` stream [#3333](https://github.com/getgrav/grav/issues/3333) [#3349](https://github.com/getgrav/grav/issues/3349)
     * Fixed copying page without changing the slug [getgrav/grav-plugin-admin#2135](https://github.com/getgrav/grav-plugin-admin/issues/2139)
+    * Fixed missing and commonly used methods when using `system.twig.undefined_functions = false` [getgrav/grav-plugin-admin#2138](https://github.com/getgrav/grav-plugin-admin/issues/2138)
 
 # v1.7.14
 ## 04/29/2021
diff --git a/system/src/Grav/Common/Twig/Extension/FilesystemExtension.php b/system/src/Grav/Common/Twig/Extension/FilesystemExtension.php
index 539fedea3..9918af856 100644
--- a/system/src/Grav/Common/Twig/Extension/FilesystemExtension.php
+++ b/system/src/Grav/Common/Twig/Extension/FilesystemExtension.php
@@ -31,7 +31,7 @@ class FilesystemExtension extends AbstractExtension
     }
 
     /**
-     * @return TwigFunction[]
+     * @return TwigFilter[]
      */
     public function getFilters()
     {
@@ -58,6 +58,7 @@ class FilesystemExtension extends AbstractExtension
             new TwigFilter('md5_file', [$this, 'md5_file']),
             new TwigFilter('sha1_file', [$this, 'sha1_file']),
             new TwigFilter('get_meta_tags', [$this, 'get_meta_tags']),
+            new TwigFilter('pathinfo', [$this, 'pathinfo']),
         ];
     }
 
@@ -91,6 +92,7 @@ class FilesystemExtension extends AbstractExtension
             new TwigFunction('md5_file', [$this, 'md5_file']),
             new TwigFunction('sha1_file', [$this, 'sha1_file']),
             new TwigFunction('get_meta_tags', [$this, 'get_meta_tags']),
+            new TwigFunction('pathinfo', [$this, 'pathinfo']),
         ];
     }
 
@@ -364,6 +366,16 @@ class FilesystemExtension extends AbstractExtension
         return get_meta_tags($filename);
     }
 
+    /**
+     * @param string $path
+     * @param int $flags
+     * @return string|string[]
+     */
+    public function pathinfo($path, $flags = PATHINFO_ALL)
+    {
+        return pathinfo($path);
+    }
+
     /**
      * @param string $filename
      * @return bool
diff --git a/system/src/Grav/Common/Twig/Extension/GravExtension.php b/system/src/Grav/Common/Twig/Extension/GravExtension.php
index d07697339..76c1bbff6 100644
--- a/system/src/Grav/Common/Twig/Extension/GravExtension.php
+++ b/system/src/Grav/Common/Twig/Extension/GravExtension.php
@@ -158,7 +158,11 @@ class GravExtension extends AbstractExtension implements GlobalsInterface
 
             // Object Types
             new TwigFilter('get_type', [$this, 'getTypeFunc']),
-            new TwigFilter('of_type', [$this, 'ofTypeFunc'])
+            new TwigFilter('of_type', [$this, 'ofTypeFunc']),
+
+            // PHP methods
+            new TwigFilter('count', 'count'),
+            new TwigFilter('array_diff', 'array_diff'),
         ];
     }
 
@@ -220,7 +224,18 @@ class GravExtension extends AbstractExtension implements GlobalsInterface
 
             // Object Types
             new TwigFunction('get_type', [$this, 'getTypeFunc']),
-            new TwigFunction('of_type', [$this, 'ofTypeFunc'])
+            new TwigFunction('of_type', [$this, 'ofTypeFunc']),
+
+            // PHP methods
+            new TwigFunction('is_numeric', 'is_numeric'),
+            new TwigFunction('is_iterable', 'is_iterable'),
+            new TwigFunction('is_countable', 'is_countable'),
+            new TwigFunction('is_null', 'is_null'),
+            new TwigFunction('is_string', 'is_string'),
+            new TwigFunction('is_array', 'is_array'),
+            new TwigFunction('is_object', 'is_object'),
+            new TwigFunction('count', 'count'),
+            new TwigFunction('array_diff', 'array_diff'),
         ];
     }