fixed some type check issues

Author: hamidrezarj

src/Filter/SearchFunctions/FilterGreaterThan.php

@@ -9,7 +9,7 @@ class FilterGreaterThan extends SearchFilter
 {
     public function apply(): Builder
     {
-        $value = ($this->filter->getDatatype() == DataType::NUMERIC) ?
+        $value = ($this->filter->getDatatype() == DataType::NUMERIC->value) ?
             (float) $this->filter->getValue() : $this->filter->getValue();
 
         return $this->query->where($this->filter->getId(), '>', $value);

src/Filter/SearchFunctions/FilterGreaterThanOrEqual.php

@@ -9,7 +9,7 @@ class FilterGreaterThanOrEqual extends SearchFilter
 {
     public function apply(): Builder
     {
-        $value = ($this->filter->getDatatype() == DataType::NUMERIC) ?
+        $value = ($this->filter->getDatatype() == DataType::NUMERIC->value) ?
             (float) $this->filter->getValue() : $this->filter->getValue();
 
         return $this->query->where($this->filter->getId(), '>=', $value);

src/Filter/SearchFunctions/FilterLessThan.php

@@ -9,7 +9,7 @@ class FilterLessThan extends SearchFilter
 {
     public function apply(): Builder
     {
-        $value = ($this->filter->getDatatype() == DataType::NUMERIC) ?
+        $value = ($this->filter->getDatatype() == DataType::NUMERIC->value) ?
             (float) $this->filter->getValue() : $this->filter->getValue();
 
         return $this->query->where($this->filter->getId(), '<', $value);

src/Filter/SearchFunctions/FilterLessThanOrEqual.php

@@ -9,7 +9,7 @@ class FilterLessThanOrEqual extends SearchFilter
 {
     public function apply(): Builder
     {
-        $value = ($this->filter->getDatatype() == DataType::NUMERIC) ?
+        $value = ($this->filter->getDatatype() == DataType::NUMERIC->value) ?
             (float) $this->filter->getValue() : $this->filter->getValue();
 
         return $this->query->where($this->filter->getId(), '<=', $value);

src/Validators/FilterValidator.php

@@ -55,7 +55,7 @@ protected function isValidSearchFunction(Filter $filter): bool
     {
         $searchFunction = $filter->getFn();
 
-        return isset($searchFunction) && in_array($searchFunction, SearchType::values());
+        return $searchFunction && in_array($searchFunction, SearchType::values());
     }
 
     protected function isValidDataType(Filter $filter): int