original_string: public static function is_json($st)
    {
      if ( \is_string($st) && !empty($st) &&
        ( (substr($st, 0, 1) === '{') || (substr($st, 0, 1) === '[') )){
        json_decode($st);
        return (json_last_error() == JSON_ERROR_NONE);
      }
      return false;
    }
code: public static function is_json($st)
    {
      if ( \is_string($st) && !empty($st) &&
        ( (substr($st, 0, 1) === '{') || (substr($st, 0, 1) === '[') )){
        json_decode($st);
        return (json_last_error() == JSON_ERROR_NONE);
      }
      return false;
    }
code_tokens: public static function is_json ( $ st ) { if ( \ is_string ( $ st ) && ! empty ( $ st ) && ( ( substr ( $ st , 0 , 1 ) === '{' ) || ( substr ( $ st , 0 , 1 ) === '[' ) ) ) { json_decode ( $ st ) ; return ( json_last_error ( ) == JSON_ERROR_NONE ) ; } return false ; }
docstring: Checks if the string is a json string.
  
  ```php
  \bbn\x::dump(\bbn\str::is_json('{"firstName": "John", "lastName": "Smith", "age": 25}'));
  // (bool) true
  ```
  
  @param string $st The string.
  @return bool
docstring_tokens: Checks if the string is a json string .