Question

What is Call Time Pass Reference? What does it do?

Answer 1

I assume you mean Call Time Pass By Reference.

In PHP, the & operator will get the reference of the variable (There is lots of info on this on stackoverflow)

Call time pass by reference is where you pass a reference as an argument to a function that doesn’t take a reference

function foo($myParam){
}

//Call Time Pass By Reference
foo(&$myArg);

This will give a warning in PHP 5.3 as it as been deprecated and it will be passed by value. The correct way to do it is to alter the function foo to take a reference

function foo(&$myParam){
}

foo($myArg); //myArg is passed by reference

The ability to preform call time pass by reference is controlled by the ini setting

allow_call_time_pass_reference

In more recent releases this is off by default.

The reason why it is bad is that the function (and reader) doesn’t know which parameters are references and which aren’t. It makes the code a lot harder to follow.