diff --git a/forms/NullableField.php b/forms/NullableField.php
index ad1489121..5fa41f50d 100644
--- a/forms/NullableField.php
+++ b/forms/NullableField.php
@@ -1,75 +1,98 @@
 <?php
+
 /**
- * NullableField is a field that wraps other fields when you want to allow the user to specify whether the value of
- * the field is null or not.
- * 
- * The classic case is to wrap a TextField so that the user can distinguish between an empty string and a null string.
+ * NullableField is a field that wraps other fields when you want to allow the user to specify
+ * whether the value of the field is null or not.
+ *
+ * The classic case is to wrap a TextField so that the user can distinguish between an empty string
+ * and a null string.
+ *
  * $a = new NullableField(new TextField("Field1", "Field 1", "abc"));
- * 
- * It displays the field that is wrapped followed by a checkbox that is used to specify if the value is null or not.
- * It uses the Title of the wrapped field for its title.
- * When a form is submitted the field tests the value of the "is null" checkbox and sets its value accordingly.
- * You can retrieve the value of the wrapped field from the NullableField as follows:
+ *
+ * It displays the field that is wrapped followed by a checkbox that is used to specify if the
+ * value is null or not. It uses the Title of the wrapped field for its title.
+ *
+ * When a form is submitted the field tests the value of the "is null" checkbox and sets its value
+ * accordingly. You can retrieve the value of the wrapped field from the NullableField as follows:
+ *
  * $field->Value() or $field->dataValue()
- * 
- * You can specify the label to use for the "is null" checkbox.  If you want to use I8N for this label then specify it
- * like this:
- * 
- * $field->setIsNullLabel(_T(SOME_MODULE_ISNULL_LABEL, "Is Null");
- * 
+ *
+ * You can specify the label to use for the "is null" checkbox. If you want to use i18n for this
+ * label then specify it like this:
+ *
+ * $field->setIsNullLabel(_T(SOME_MODULE_ISNULL_LABEL, "Is Null"));
+ *
  * @author Pete Bacon Darwin
+ *
  * @package forms
  * @subpackage fields-basic
  */
 class NullableField extends FormField {
 	/**
 	 * The field that holds the value of this field
+	 *
 	 * @var FormField
 	 */
 	protected $valueField;
-		
+
 	/**
 	 * The label to show next to the is null check box.
+	 *
 	 * @var string
 	 */
 	protected $isNullLabel;
-	
 
 	/**
 	 * Create a new nullable field
-	 * @param $valueField
-	 * @return NullableField
+	 *
+	 * @param FormField $valueField
+	 * @param null|string $isNullLabel
 	 */
 	public function __construct(FormField $valueField, $isNullLabel = null) {
 		$this->valueField = $valueField;
-		$this->isNullLabel = $isNullLabel;
-		if ( is_null($this->isNullLabel) ) {
-			// Set a default label if one is not provided.
+
+		if(isset($isNullLabel)) {
+			$this->setIsNullLabel($isNullLabel);
+		} else {
 			$this->isNullLabel = _t('NullableField.IsNullLabel', 'Is Null');
 		}
-		parent::__construct($valueField->getName(), $valueField->Title(), $valueField->Value(),
-			$valueField->getForm(), $valueField->RightTitle());
-		$this->readonly = $valueField->isReadonly();
+
+		parent::__construct(
+			$valueField->getName(),
+			$valueField->Title(),
+			$valueField->Value()
+		);
+
+		$this->setForm($valueField->getForm());
+		$this->setRightTitle($valueField->RightTitle());
+		$this->setReadonly($valueField->isReadonly());
 	}
-	
+
 	/**
 	 * Get the label used for the Is Null checkbox.
+	 *
 	 * @return string
 	 */
 	public function getIsNullLabel() {
 		return $this->isNullLabel;
 	}
+
 	/**
 	 * Set the label used for the Is Null checkbox.
+	 *
 	 * @param $isNulLabel string
+	 *
+	 * @return $this
 	 */
-	public function setIsNullLabel(string $isNulLabel){
+	public function setIsNullLabel($isNulLabel) {
 		$this->isNullLabel = $isNulLabel;
+
 		return $this;
 	}
-	
+
 	/**
 	 * Get the id used for the Is Null check box.
+	 *
 	 * @return string
 	 */
 	public function getIsNullId() {
@@ -77,53 +100,80 @@ class NullableField extends FormField {
 	}
 
 	/**
-	 * (non-PHPdoc)
-	 * @see framework/forms/FormField#Field()
+	 * @param array $properties
+	 *
+	 * @return string
 	 */
 	public function Field($properties = array()) {
-		if ( $this->isReadonly()) {
+		if($this->isReadonly()) {
 			$nullableCheckbox = new CheckboxField_Readonly($this->getIsNullId());
 		} else {
 			$nullableCheckbox = new CheckboxField($this->getIsNullId());
 		}
+
 		$nullableCheckbox->setValue(is_null($this->dataValue()));
 
-		return $this->valueField->Field() . ' ' . $nullableCheckbox->Field()
-			. '&nbsp;<span>' . $this->getIsNullLabel().'</span>';
+		return sprintf(
+			'%s %s&nbsp;<span>%s</span>',
+			$this->valueField->Field(),
+			$nullableCheckbox->Field(),
+			$this->getIsNullLabel()
+		);
 	}
 
 	/**
 	 * Value is sometimes an array, and sometimes a single value, so we need to handle both cases
+	 *
+	 * @param mixed $value
+	 * @param null|array $data
+	 *
+	 * @return $this
 	 */
 	public function setValue($value, $data = null) {
-		if ( is_array($data) && array_key_exists($this->getIsNullId(), $data) && $data[$this->getIsNullId()] ) {
+		$id = $this->getIsNullId();
+
+		if(is_array($data) && array_key_exists($id, $data) && $data[$id]) {
 			$value = null;
 		}
+
 		$this->valueField->setValue($value);
+
 		parent::setValue($value);
 
 		return $this;
 	}
-	
+
 	/**
-	 * (non-PHPdoc)
-	 * @see forms/FormField#setName($name)
+	 * @param string $name
+	 *
+	 * @return $this
 	 */
 	public function setName($name) {
-		// We need to pass through the name change to the underlying value field.
 		$this->valueField->setName($name);
+
 		parent::setName($name);
 
 		return $this;
 	}
 
 	/**
-	 * (non-PHPdoc)
-	 * @see framework/forms/FormField#debug()
+	 * @return string
 	 */
 	public function debug() {
-		$result = "$this->class ($this->name: $this->title : <font style='color:red;'>$this->message</font>) = ";
-		$result .= (is_null($this->value)) ? "<<null>>" : $this->value;
-		return result;
+		$result = sprintf(
+			'%s (%s: $s : <span style="color: red">%s</span>) = ',
+			$this->class,
+			$this->name,
+			$this->title,
+			$this->message
+		);
+
+		if($this->value === null) {
+			$result .= "<<null>>";
+		} else {
+			$result .= (string) $this->value;
+		}
+
+		return $result;
 	}
 }