Comments

Any serious programmer will say you that a good program is a commented program. Comments are destinated to the reader only and are ignored by the compiler.
To add a comment, use the ` symbol.

 ` this is a full line comment
 print x ` this is a comment at end of line
     
     A such comment can't be followed by any statement.
     The compiler recognizes also the C++ symbol: //
 // this is a one-line comment as in C++.
     
     A multi-line comment begins with /* and ends with */

Example:

/*
     inside these markers, anything is ignored by the compiler
*/

Comments are not kept into the target language. You can make them persistent by doubling the symbol ` in this manner:

`` this is a persistent comment

The compiler could recognize code following the end of a such comment, but this is just not good programming style!

Persistency

Comments defining by these codes:

  `
  //
  /* */

are not kept into the generated target code, neither Php nor C++.
For a comment to be kept, the comment symbol must be doubled:

  ``

Examples of comments. int x = 10       ` not persistent comment
print x            `` persistent comment
C++ generated code: int x = 10;  
cout << x << "\n";    `` persistent comment