I doubt you will be able to replace some words from a string in one table, with words from another table, though a table is a good place to store the replacements.
To do this in PHP you would construct an array of translation terms…
You then need to run that array over your text and replace the key words.
$translations = array(
"hard"=>"dur",
"email"=>"courriel",
//... and so on
);
$text = "I find it really hard to write email in French.";
var_dump($translations);
foreach( $translations as $k=>$v){
$text = str_ireplace(" " . $k ." ", " ". $v ." ",$text);
}
echo $text;
// I find it really dur to write courriel in French.
This is incredibly oversimplified.
It could be improved e.g. by checking to see if the $k exists in the string before calling replace and so on - but should serve as an example.
There are many edge cases this does not cope with, say a sentence ends in hard. or is followed by a comma hard, [ EDIT use str_ireplace instead discount this-> ] or starts a sentence Hard times await…
There are probably other better ways of doing translations… does this answer your question?