How to string two variables together in php

I am new to php. And string concatenation is difficult for me. I want to concatenate the following string:

$branch = 'apple';
$rules = "(product=='iphone')andManufacturer==".$branch;
// result "(product == 'iphone')andManufacturer ==apple"

But the string I want:

"(product=='iphone')andManufacturer=='apple'"

Thanks.

>Solution :

Try this(Added single quote to the string):

$branch = 'apple';
$rules = "(product=='iphone')andManufacturer=='".$branch."'";
echo $rules;

Another solution(Wrap the single quotes in double quotes to branch variable):

$branch = "'apple'";
$rules = "(product=='iphone')andManufacturer==".$branch;
echo $rules;

OUTPUT:

(product=='iphone')andManufacturer=='apple'