It will work when you format it like so:
$tPerson_SQLinsert = <<<SQL
INSERT INTO tPerson (Salutation, FirstName, LastName, Tel, companyID)
VALUES ("$Salutation", "$FirstName", "$LastName", "$Tel", "$companyID")
SQL;
I.e. the final delimiter should start in column 1.
See docs (in the warning block): https://www.php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc