New form_validation rule: 'differs'
Added new validation rule 'differs'. It checks if the value of a field differs from the value of another field.
diff --git a/system/language/english/form_validation_lang.php b/system/language/english/form_validation_lang.php
index cf1b3b5..6ff0cc2 100644
--- a/system/language/english/form_validation_lang.php
+++ b/system/language/english/form_validation_lang.php
@@ -42,6 +42,7 @@
 $lang['integer']				= 'The %s field must contain an integer.';
 $lang['regex_match']			= 'The %s field is not in the correct format.';
 $lang['matches']				= 'The %s field does not match the %s field.';
+$lang['differs']        		= 'The %s field must differ from the %s field.';
 $lang['is_unique'] 				= 'The %s field must contain a unique value.';
 $lang['is_natural']				= 'The %s field must only contain digits.';
 $lang['is_natural_no_zero']		= 'The %s field must only contain digits and must be greater than zero.';
diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index fccc12a..6db5bb4 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -971,6 +971,19 @@
 	// --------------------------------------------------------------------
 
 	/**
+	 * Differs from another field
+	 *
+	 * @param	string
+	 * @param	string	field
+	 * @return	bool
+	 */
+	public function differs($str, $field)
+	{
+		return ! (isset($this->_field_data[$field]) && $this->_field_data[$field]['postdata'] === $str);
+	}
+
+	// --------------------------------------------------------------------
+	/**
 	 * Is Unique
 	 *
 	 * Check if the input value doesn't already exist