When using SQL in PHP you have used code like this (sqlprintr.php in beginnerssite):

$sqlResult=mysqli_query($dbconnection, "SELECT personalName, familyName FROM first;") or die("Selecting data failed: ".mysqli_error($dbconnection));

It is a fairly long line and can get worse with more advanced queries.  Therefore you should at least consider doing it like this:

$sqlQuery="SELECT personalName, familyName FROM first;";

$sqlError="Selecting data failed: ";

$sqlResult=mysqli_query($dbconnection, $sqlQuery) or die($sqlError.mysqli_error($dbconnection));

There may be more lines but each one is shorter and therefore easier to see and to edit.

This concept of splitting the data from the code which actually does things is used by almost all proper developers.  It makes no real difference to execution but it may help you to understand the code.  Consider trying it and deciding for yourself but most code examples you come across will do it the enw way.