Should I pass my $mysqli variable to each function?
User-defined functions have their own variable scope in PHP. You need to pass $mysqli to the function as a parameter, or start the function with global $mysqli.
This exact problem is given as an example on the Variable scope page:
However, within user-defined functions a local function scope is introduced. Any variable used inside a function is by default limited to the local function scope. For example, this script will not produce any output because the echo statement refers to a local version of the $a variable, and it has not been assigned a value within this scope. You may notice that this is a little bit different from the C language in that global variables in C are automatically available to functions unless specifically overridden by a local definition. This can cause some problems in that people may inadvertently change a global variable. In PHP global variables must be declared global inside a function if they are going to be used in that function.
<?php$a = 1; /* global scope */ function test(){ echo $a; /* reference to local scope variable */ } test();?>
cannot manage it to work without passing to the function the $mysqli variable, but this was not necessary when I used mysql_* deprecated functions!
That is not really correct. Even in the old mysql_* function you actually had to pass the link identifier if you needed to specify to which database connection you were relating to, e.g.:
$result = mysql_query($sql, $link);Also what this example shows, you had to pass along the $result, too. In case you did left out the $link parameter:
$result = mysql_query($sql);The mysql extension did look internally for the last used connection. If none would have been found, it would have created a new one with the parameters set in php.ini. That just for your information to better understood why and how this worked in the past.