PHP : check variables line by line in text file and store unique variables

I store my variables in text file.Next I get another vars, they most store in text file if they arent duplicate and old data must be clear. Check each new vars by vars stored in file. and only store unique vars.

for example first I have:

hello
begin开发者_JAVA百科
start
all page
thanks

in text file and I get new vars :

buy
have
start
animate
hello

finally stored vars in text file must be: buy have animate

(ignored start & hello)

THXA

---

This is for file handling.

$myFile = "testFile1.txt";
$fh = fopen($myFile, 'r');
$theData = fread($fh, filesize($myFile));
fclose($fh);

Now, perform your comparison between the the data sets.