How does PHP compare the variable size?

PHP: How to compare the variable size php obtains the value of field A through row in the previous section $ A $ row [A] & nbsp; wants to compare the word $ A and "none, if they are equal, "none" is displayed in red. I would like to compare how to write it here. ------ Solution ------------------ $ s & nbsp; If you want to compare the word $ A and "none", "none" indicates red if they are equal. How does PHP compare the variable size?
Php obtains the value of field A through row in the previous section.
$ 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.

------ 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 );