How to compare the variable size in PHP-php Tutorial

PHP: How to compare the variable size php returns the value of field A through row
$ A = $ row ['A'];
If you want to compare $ A and "none", if they are equal, "none" is displayed in red. I would like to compare how to write it here.

Reply to discussion (solution)

$ S = 'to compare the word $ A and "none". if they are the same, "none" is displayed in red. Could you tell me how to write it here? '; $ A = 'none'; echo preg_replace ("/$ A/",' $ 0', $ s );

Don't understand, great God

Oh, thank you.