Add get all css functions method

src/CSSList/CSSBlockList.php

@@ -140,4 +140,27 @@ protected function allSelectors(array &$aResult, $sSpecificitySearch = null)
             }
         }
     }
+
+    /**
+     * @param CSSList|Rule|RuleSet|Value $oElement
+     * @param array<int, CSSFunction> $aResult
+     *
+     * @return void
+     */
+    protected function allFunctions($oElement, array &$aResult)
+    {
+        if ($oElement instanceof CSSBlockList) {
+            foreach ($oElement->getContents() as $oContent) {
+                $this->allFunctions($oContent, $aResult);
+            }
+        } elseif ($oElement instanceof RuleSet) {
+            foreach ($oElement->getRules() as $oRule) {
+                $this->allFunctions($oRule, $aResult);
+            }
+        } elseif ($oElement instanceof Rule) {
+            $this->allFunctions($oElement->getValue(), $aResult);
+        } elseif ($oElement instanceof CSSFunction) {
+            $aResult[] = $oElement;
+        }
+    }
 }

src/CSSList/Document.php

@@ -109,6 +109,26 @@ public function getSelectorsBySpecificity($sSpecificitySearch = null)
         return $aResult;
     }
 
+    /**
+     * Returns all `CSSFunction` objects recursively found in the tree, no matter how deeply nested the rule sets are.
+     * 
+     * @param CSSList|RuleSet|string $mElement
+     *        the `CSSList` or `RuleSet` to start the search from (defaults to the whole document).
+     *        If a string is given, it is used as rule name filter.
+     *
+     * @return array<int, CSSFunction>
+     */
+    public function getAllFunctions($mElement = null)
+    {
+        if ($mElement === null) {
+            $mElement = $this;
+        }
+        /** @var array<int, Value> $aResult */
+        $aResult = [];
+        $this->allFunctions($mElement, $aResult);
+        return $aResult;
+    }
+
     /**
      * Expands all shorthand properties to their long value.
      *