---input---
<?php $x="{\""; ?>

---tokens---
'<?php'       Comment.Preproc
' '           Text
'$x'          Name.Variable
'='           Operator
'"'           Literal.String.Double
'{'           Literal.String.Double
'\\"'         Literal.String.Escape
'"'           Literal.String.Double
';'           Punctuation
' '           Text
'?>'          Comment.Preproc
'\n'          Other