I have found a way to insert data into a postgresql database using php. Therefore, I used the following syntax:
$sql = "INSERT INTO genes (id,gene,plasmid,accessionnumber,plasmidname) VALUES ('".$var_id."','".$var_gene."','".$var_ACC."','".$var_PN."')";
For some reason, this the only way it works. Why do I need to add the point and why do I need double and single brackets and not just the single brackets?