debug_zval_dump

(PHP 4 >= 4.2.0, PHP 5, PHP 7)

Dumps a string representation of an internal zend value to output

void debug_zval_dump ( mixed $variable [, mixed $... ] )

Dumps a string representation of an internal zend value to output.

Parameters:

variable

The variable being evaluated.

Returns:

No value is returned.

Examples:

debug_zval_dump() example

<?php
$var1 = 'Hello World';
$var2 = '';
 
$var2 =& $var1;
 
debug_zval_dump(&$var1);
?>

The above example will output:

&string(11) "Hello World" refcount(3)

The above example will output:

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
?>

string(11) "Hello World" refcount(1)

The above example will output:

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);
?>

string(11) "Hello World" refcount(2)