To indicate an argument is passed by reference to the function, what character should I use before the argument in the parenthesis??
I'm reading in one book:
When you use a function that passes an argument by reference, do not prefix the argument with an ampersand. The ampersand is used only in the function definition.
So what character is used? I'm just confused on this entirely.
As explained in the documentation, to define a function taking arguments by reference you prefix each such argument with &:
function getsArgumentByRef(&$argument) { /* ... */ }
When calling the function, do not use an ampersand:
$result = getsArgumentByRef($input);
An ampersand (&) is used in the function definition like:
function something( &$parameter ){ ... }
But nothing is used in the call:
$variable = 3;
$other = something( $variable );
The & ampersand is used, as Jon mentioned in his comment.
However, the important part to take away from this in my opinion is what they mean by "...function definition."
The function definition is the actual source code that completes your function's task, or in the case of an interface what dependencies that function has.
This is a function definition:
function doCoolStuff(array &$data) {
...
}
The important part here isn't the implementation but the name doCoolStuff and the need for an array parameter to be passed.
Calling code is when you actually use the function.
$data = ('favorite_site' => 'stackoverflow');
doCoolStuff($data);
Notice, in the function definition up top there is an ampersand before the parameter name, this indicates the array is passed by reference. Changes made to the array in the function change the array that was passed. Also notice, there was no need to use the & in the calling code, the pass-by-reference is taken care of by the function definition.