Adding a json validator.

README.md

@@ -50,6 +50,7 @@ bool endswith(mixed $input, string $match)
 bool contains(mixed $input, string $match)
 bool regex(mixed $input, string $regex)
 bool inlist(mixed $input, array $list)
+bool json(mixed $input)
 ```
 
 ### Validation Engine

src/Validator.php

@@ -242,4 +242,15 @@ public static function inlist($input = null, $list = [])
 
 		return in_array($input, $list);
 	}
+
+	public static function json($input = null)
+	{
+		if (empty($input)) {
+			return true;
+		}
+
+		$attempted_parsed_json = json_decode($input, true);
+
+		return ( $attempted_parsed_json !== null );
+	}
 }

tests/ValidatorTests.php

@@ -300,4 +300,24 @@ public function testShouldPassInlist()
 		$this->assertTrue(Validator::inlist(null, ['ABC','DEF']));
 		$this->assertTrue(Validator::inlist('ABC', ['ABC','DEF']));
 	}
+
+	public function testShouldFailJson()
+	{
+		$this->assertFalse(Validator::json('asd;flkj'));
+	}
+
+	public function testShouldPassJson()
+	{
+		$this->assertTrue(Validator::json('{"widget": {
+		    "debug": "on",
+		    "window": {
+		        "title": "Sample Konfabulator Widget",
+		        "name": "main_window",
+		        "width": 500,
+		        "height": 500
+		    }}}'
+		));
+
+		$this->assertTrue(Validator::json('{}'));
+	}
 }