How do curly braces affect MySQL syntax?

I accidentally put a PHP statement in MySQL:

select * from info where id={${intval(17a)}}

      

        
        
        
      

    

MySQL gave me an error message:

ERROR 1054 (42S22): Unknown column '17a' in 'where clause'

Why is MySQL not giving a syntax error, empty result, or showing {${intval(17a)}}

in an error message? Column in value id

is equal {${intval(17a)}}

but mysql is talking about column '17a'

? Are curly braces and dollar sign special characters in MySQL?

Demo