string-variable production rule not used?

[nbloomf]

In the grammar, the string-variable production rule is not used.

Looking at https://github.com/php/php-src/blob/0720313bd452adf451173574e97fd761f90623a2/Zend/zend_language_parser.y#L1223, I think it should be a summand of dq-char.

[nikic]

Should probably be in both dq-char and hd-char.