Here is a quick tip if you need to recursively grep a directory for files containing a certain string and replace the entire line containing that string here's one way to accomplish that.
grep -lr wngzhxknyp * | xargs sed -i 's/.*wngzhxknyp.*/<?php/'
The -lr switches make grep searche the current directory recursively (the -r) and only returns the filenames (the -l) that contain the matching string "wngzhxknyp". When we pipe the resulting filenames to sed we use sed to search and replace any lines containing "wngzhxknyp" with "<?php".