What are the best practices for initializing variables in PHP when no value is assigned?

When initializing variables in PHP without assigning a value, it is best practice to explicitly set them to NULL to avoid any potential issues. This ensures that the variable is defined but does not have a specific value until one is assigned later in the code.

// Initializing variables to NULL
$variable1 = NULL;
$variable2 = NULL;
$variable3 = NULL;