In PHP, there is no concept of a "reference variable" in the same way as in some other programming languages like C++. However, PHP does support references in the form of reference assignment and pass-by-reference for function arguments.

Here's how you can use references in PHP:

1. **Reference Assignment**:

   You can create a reference to a variable using the `&` symbol. When you assign a variable by reference, it means that both variables refer to the same data in memory. Any changes made to one variable will affect the other.

   ```php

   $original = 10;
   $reference = &$original;
   $reference = 20; // Changes $original as well
   echo $original; // Output: 20

   ```

2. **Passing by Reference**:

   In PHP, function arguments are passed by value by default, which means a copy of the variable's value is passed into the function. However, you can pass a variable by reference by using the `&` symbol in both the function definition and the function call. This allows the function to modify the original variable.

   ```php

   function multiplyByTwo(&$value) {
       $value *= 2;
   }
   
   $num = 5;
   multiplyByTwo($num);
   echo $num; // Output: 10

   ```

   Note that while passing by reference can be useful, it should be used judiciously as it can make code harder to understand and debug.

3. **Returning by Reference**:

   You can also return a reference from a function. This can be used to modify variables outside of the function scope.

   ```php

   function &getArrayItem(&$array, $index) {
       return $array[$index];
   }
   
   $myArray = [1, 2, 3];
   $item = &getArrayItem($myArray, 1);
   $item = 10; // Modifies $myArray to [1, 10, 3]

   ```

In PHP, references can be powerful, but they should be used with caution to avoid unexpected side effects and make your code more readable and maintainable.