What is the issue with variable passing in PHP functions as described in the forum thread?

The issue with variable passing in PHP functions described in the forum thread is that when passing a variable by value to a function, any changes made to the variable within the function will not affect the original variable outside of the function. To solve this issue and have the changes reflected outside the function, you can pass the variable by reference using the '&' symbol before the variable name in the function parameter list.

// Original code with variable passed by value
$number = 10;
function doubleNumber($num) {
    $num = $num * 2;
}
doubleNumber($number);
echo $number; // Output will be 10

// Fixed code with variable passed by reference
$number = 10;
function doubleNumber(&$num) {
    $num = $num * 2;
}
doubleNumber($number);
echo $number; // Output will be 20