debug_zval_dump in PHP

debug_zval_dump — Dumps a string representation of an internal zend value to output
Syntax:
void debug_zval_dump ( mixed $variable [, mixed $... ] )
Parameters:
variable: The variable being evaluated.
Return Values:
No value is returned.
Example:
<?php
$var1 = 'Hello World';
$var2 = '';
$var2 =& $var1;
debug_zval_dump(&$var1);
?>

O/P:&string(11) "Hello World" refcount(3)

Note: 
Beware the refcount
    The refcount value returned by this function is non-obvious in certain circumstances. 
    For example, a developer might expect the above example to indicate a refcount of 2. 
    The third reference is created when actually calling debug_zval_dump().
    This behavior is further compounded when a variable is not passed to debug_zval_dump() by reference. 
    To illustrate, consider a slightly modified version of the above example:
    <?php
    $var1 = 'Hello World';
    $var2 = '';
    $var2 =& $var1;
    debug_zval_dump($var1); // not passed by reference, this time
    ?>

O/P:string(11) "Hello World" refcount(1)
   Why refcount(1)? Because a copy of $var1 is being made, when the function is called.
    This function becomes even more confusing when a variable with a refcount of 1 is passed (by copy/value):
    <?php
    $var1 = 'Hello World';
    debug_zval_dump($var1);
    ?>
    O/P:string(11) "Hello World" refcount(2)
    A refcount of 2, here, is extremely non-obvious. 
        Especially considering the above examples. So what's happening?
    When a variable has a single reference (as did $var1 before it was used as an argument to debug_zval_dump()), 
        PHP's engine optimizes the manner in which it is passed to a function. 
        Internally, PHP treats $var1 like a reference (in that the refcount is increased for the scope of this function), 
        with the caveat that if the passed reference happens to be written to, a copy is made, but only at the moment of writing. 
        This is known as "copy on write."
    So, if debug_zval_dump() happened to write to its sole parameter (and it doesn't), then a copy would be made. 
        Until then, the parameter remains a reference, causing the refcount to be incremented to 2 for the scope of the function call.