Most basic implementation for i18n can be done through language files. It involve 3 major steps
Step 1: Define language files
For your example, define 3 files en.php, fr.php and ar.php (or more for more languages). Better keep all these files in 'language' folder. File contents will be like
<?PHP
$LANG_LABEL_TITLE = "Title in specific language";
step 2: Include language file
There must be a common script for all your web accessible files; central controller or at lease a common header. In that file, detect default browser language and set it in session. Again include required language file there.
step 3: Use labels
Once you have required language file included, simple use the label at required position like
<title><?PHP echo $LANG_LABEL_TITLE; ?></title>
Again this is the most basic implementation. Go through it and if you stuck somewhere, ask question specific to that part.