isJson() function, with tests

README.md

@@ -23,6 +23,7 @@ A PHP library with a variety of string manipulation functions with multibyte sup
     * [isAlpha](#isalpha)
     * [isAlphanumeric](#isalphanumeric)
     * [isBlank](#isblank)
+    * [isJson](#isjson)
     * [isHexadecimal](#ishexadecimal)
     * [isLowerCase](#islowercase)
     * [isUpperCase](#isuppercase)
@@ -338,6 +339,19 @@ S::create("\n\t  \v\f")->isBlank();
 S::isBlank("\n\t  \v\f");  // true
 ```
 
+#### isJson
+
+$stringy->isJson()
+
+S::isJson(string $str [, string $encoding ])
+
+Returns true if the string is JSON, false otherwise.
+
+```php
+S::create('{"foo":"bar"}')->isJson();
+S::isJson('{"foo":"bar"}');  // true
+```
+
 #### isHexadecimal
 
 $stringy->isHexadecimal()

src/Stringy/StaticStringy.php

@@ -624,6 +624,18 @@ class StaticStringy
         return Stringy::create($str, $encoding)->isBlank();
     }
 
+    /**
+     * Returns true if the string is JSON, false otherwise.
+     *
+     * @param   string   $str       String to check
+     * @param   string   $encoding  The character encoding
+     * @return  bool     Whether or not $str is JSON
+     */
+    public static function isJson($str, $encoding = null)
+    {
+        return Stringy::create($str, $encoding)->isJson();
+    }
+
     /**
      * Returns true if the string contains only lower case chars, false otherwise.
      *

src/Stringy/Stringy.php

@@ -994,6 +994,19 @@ class Stringy
         return $this->matchesPattern('^([[:space:]])*$');
     }
 
+    /**
+     * Returns true if the string is JSON, false otherwise.
+     *
+     * @return  bool  Whether or not $str is JSON
+     */
+    public function isJson()
+    {
+        json_decode($this->str);
+
+        return json_last_error() == JSON_ERROR_NONE && $this->matchesPattern("^\W*[\[{].+$");
+    }
+
+
     /**
      * Returns true if the string contains only lower case chars, false otherwise.
      *

tests/Stringy/CommonTest.php

@@ -766,6 +766,33 @@ abstract class CommonTest extends PHPUnit_Framework_TestCase
         return $testData;
     }
 
+    public function stringsForIsJson()
+    {
+        $testData = array(
+            array(false, ''),
+            array(false, '123'),
+            array(true, '{"foo": "bar"}'),
+            array(false, '{"foo":"bar",}'),
+            array(false, '{"foo"}'),
+            array(false, '["foo": "bar"]'),
+            array(true, '["foo"]'),
+            array(false, '{"foo"}'),
+            array(false, '{"foo": "bar"]'),
+            array(true, ' { "foo" : "bar" } '),
+            array(false, '123', 'UTF-8'),
+            array(true, '{"foo": "bar"}', 'UTF-8'),
+            array(false, '{"foo":"bar",}', 'UTF-8'),
+            array(false, '{"foo"}', 'UTF-8'),
+            array(false, '["foo": "bar"]', 'UTF-8'),
+            array(true, '["foo"]', 'UTF-8'),
+            array(false, '{"foo"}', 'UTF-8'),
+            array(false, '{"foo": "bar"]', 'UTF-8'),
+            array(true, '  {  "foo"  :  "bar"  }  ', 'UTF-8'),
+        );
+
+        return $testData;
+    }
+
     public function stringsForIsLowerCase()
     {
         $testData = array(

tests/Stringy/StaticStringyTest.php

@@ -461,6 +461,16 @@ class StaticStringyTestCase extends CommonTest
         $this->assertInternalType('boolean', $result);
         $this->assertEquals($expected, $result);
     }
+    
+    /**
+     * @dataProvider stringsForIsJson
+     */
+    public function testIsJson($expected, $str, $encoding = null)
+    {
+        $result = S::isJson($str, $encoding);
+        $this->assertInternalType('boolean', $result);
+        $this->assertEquals($expected, $result);
+    }
 
     /**
      * @dataProvider stringsForIsLowerCase

tests/Stringy/StringyTest.php

@@ -538,6 +538,18 @@ class StringyTestCase extends CommonTest
         $this->assertEquals($str, $stringy);
     }
 
+    /**
+     * @dataProvider stringsForIsJson
+     */
+    public function testIsJson($expected, $str, $encoding = null)
+    {
+        $stringy = S::create($str, $encoding);
+        $result = $stringy->isJson();
+        $this->assertInternalType('boolean', $result);
+        $this->assertEquals($expected, $result);
+        $this->assertEquals($str, $stringy);
+    }
+
     /**
      * @dataProvider stringsForIsLowerCase
      */