Throw exception on mixed data type arrays

Modified the parser so as to throw an exception on encountering mixed
data types within an array. Also corrected the extended.toml to prevent
from throwing this exception because of malformed key "key"

src/toml.php

@@ -256,7 +256,7 @@ class Toml
             }
         }
         // Datetime. Parsed to UNIX time value.
-        elseif(preg_match('/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/', $val))
+        elseif(self::isISODate($val))
         {
             $parsedVal = strtotime($val);
         }
@@ -313,6 +313,9 @@ class Toml
                         $result[] = self::parseValue( trim($buffer) );
                     }
 
+                    if (!self::checkDataType($result)) {
+                        throw new Exception('Data types cannot be mixed in an array: ' . $buffer);
+                    }
                     // Skip first and las brackets. We're finish.
                     return $result;
                 }
@@ -325,6 +328,9 @@ class Toml
             if( $val[$i] == ',' && !$openString && $openBrackets == 1)
             {
                 $result[] = self::parseValue( trim($buffer) );
+                if (!self::checkDataType($result)) {
+                    throw new Exception('Data types cannot be mixed in an array: ' . $buffer);
+                }
                 $buffer = '';
             }
             else
@@ -337,4 +343,57 @@ class Toml
         throw new Exception('Wrong array definition: ' . $val);
     }
 
+    /**
+     * Function that checks the data type of the first and last elements of an array, 
+     * and returns false if they don't match
+     * 
+     * @param  (array) $array 
+     * 
+     * @return boolean
+     */
+    private static function checkDataType($array) {
+
+        if(count($array) <= 1) 
+            return true;
+
+        $last = count($array) - 1;
+
+        $type = self::getCustomDataType($array[$last]);
+
+        if ($type != self::getCustomDataType($array[0])) {
+            return false;
+        } else {
+            return true;
+        }     
+
+    }
+
+    /**
+     * Returns the data type of a variable
+     * 
+     * @param  (mixed) $val
+     * @return (string) Data type of value
+     */
+    private static function getCustomDataType($val) {
+        
+        $val = (!is_array($val)) ? trim($val) : $val;
+
+        if (!is_array($val) && self::isISODate($val)) {
+                $type = "date";
+        } else {
+                $type = gettype($val);
+        }
+
+        return $type;
+    }
+
+    /**
+     * Return whether the given value is a valid ISODate
+     * @param  (string)  $val
+     * @return boolean
+     */
+    private static function isISODate($val) {
+        return preg_match('/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/', $val);
+    }
+
 }

tests/extended.toml

@@ -31,7 +31,9 @@ data = [ ["gamma", "delta"], [1, 2] ] # just an update to make sure parsers supp
 
 # Multi-line array check
 key = [
+  [
   1, 2, 3,
+  ],
   [
     1979-05-27T07:32:00Z,
     1979-05-27T07:32:00Z