src/Validate.php
public function isValidJsonpCallback($subject)
    {
        $identifier_syntax
          = '/^[$_\p{L}][$_\p{L}\p{Mn}\p{Mc}\p{Nd}\p{Pc}\x{200C}\x{200D}]*+$/u';

        $reserved_words = array('break', 'do', 'instanceof', 'typeof', 'case',
          'else', 'new', 'var', 'catch', 'finally', 'return', 'void', 'continue',
          'for', 'switch', 'while', 'debugger', 'function', 'this', 'with',
          'default', 'if', 'throw', 'delete', 'in', 'try', 'class', 'enum',
          'extends', 'super', 'const', 'export', 'import', 'implements', 'let',
          'private', 'public', 'yield', 'interface', 'package', 'protected',
          'static', 'null', 'true', 'false');

        return preg_match($identifier_syntax, $subject)
            && ! in_array(mb_strtolower($subject, 'UTF-8'), $reserved_words);
    }
public function isValidJsonpCallback($subject)
    {
        $identifier_syntax
          = '/^[$_\p{L}][$_\p{L}\p{Mn}\p{Mc}\p{Nd}\p{Pc}\x{200C}\x{200D}]*+$/u';

        $reserved_words = array('break', 'do', 'instanceof', 'typeof', 'case',
          'else', 'new', 'var', 'catch', 'finally', 'return', 'void', 'continue',
          'for', 'switch', 'while', 'debugger', 'function', 'this', 'with',
          'default', 'if', 'throw', 'delete', 'in', 'try', 'class', 'enum',
          'extends', 'super', 'const', 'export', 'import', 'implements', 'let',
          'private', 'public', 'yield', 'interface', 'package', 'protected',
          'static', 'null', 'true', 'false');

        return preg_match($identifier_syntax, $subject)
            && ! in_array(mb_strtolower($subject, 'UTF-8'), $reserved_words);
    }
public function isValidJsonpCallback ( $ subject ) { $ identifier_syntax = '/^[$_\p{L}][$_\p{L}\p{Mn}\p{Mc}\p{Nd}\p{Pc}\x{200C}\x{200D}]*+$/u' ; $ reserved_words = array ( 'break' , 'do' , 'instanceof' , 'typeof' , 'case' , 'else' , 'new' , 'var' , 'catch' , 'finally' , 'return' , 'void' , 'continue' , 'for' , 'switch' , 'while' , 'debugger' , 'function' , 'this' , 'with' , 'default' , 'if' , 'throw' , 'delete' , 'in' , 'try' , 'class' , 'enum' , 'extends' , 'super' , 'const' , 'export' , 'import' , 'implements' , 'let' , 'private' , 'public' , 'yield' , 'interface' , 'package' , 'protected' , 'static' , 'null' , 'true' , 'false' ) ; return preg_match ( $ identifier_syntax , $ subject ) && ! in_array ( mb_strtolower ( $ subject , 'UTF-8' ) , $ reserved_words ) ; }
Check if callback is valid
@link http://www.geekality.net/2010/06/27/php-how-to-easily-provide-json-and-jsonp/ source
@param string $subject
@return boolean
Check if callback is valid