PHP Variable Handling debug_zval_dump() Function

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The PHP Variable Handling debug_zval_dump() function is used to return a string representation of an internal zval(Zend value) structure to output. This is mostly useful for understanding or debugging implementation details of the Zend Engine or PHP extensions.

This function is mostly used for advanced debugging or to learn how PHP handles variables in the background. It is not commonly used in programming, but it can be useful when working with PHP extensions or trying to understand memory usage and references in PHP.

Syntax

Here is the syntax of the PHP Variable Handling debug_zval_dump() function −

void debug_zval_dump ( mixed $value , mixed $values )

Parameters

Below are the parameters of the debug_zval_dump() function −

• $value − It is the variable or value to dump.

• $values − Further variables or values to dump.

Return Value

The debug_zval_dump() function does not return any value.

PHP Version

First introduced in core PHP 4.2.0, the debug_zval_dump() function continues to function easily in PHP 5, PHP 7, and PHP 8.

Example 1

This program uses PHP Variable Handling debug_zval_dump() function to dump the internal structure of a simple string variable.

<?php
  // Mention variable here
  $var = "Hello, PHP!";
  debug_zval_dump($var);
?> 

Output

This will generate the below output −

string(11) "Hello, PHP!" interned

Example 2

Here we will show you the basic example of the debug_zval_dump() function to create a standard absolute deviation of an array.

  <?php
  // Mention variables here
  $var1 = 'Welcome';
  $var1 .= ' Tutorialspoint';
  $var2 = $var1;
  debug_zval_dump($var1);
  ?>

Output

This will produce following result −

string(21) "Welcome Tutorialspoint" refcount(3)

Example 3

Now the below code shows how to use debug_zval_dump() function with an array to check its structure.

<?php
  // Define an array here
  $array = [1, 2, 3, "PHP"];
  
  debug_zval_dump($array);
?> 

Output

This will create the below output −

array(4) refcount(3){ [0]=> int(1) [1]=> int(2) [2]=> int(3) [3]=> string(3) "PHP" refcount(1) }

Example 4

In the following example, we are using the debug_zval_dump() function to highlight how it can be used to track reference changes in variables.

<?php
   $a = "PHP";
   // Reference assignment
   $b = &$a; 

   debug_zval_dump($a); 
   debug_zval_dump($b); 
?> 

Output

Following is the output of the above code −

string(3) "PHP" interned string(3) "PHP" interned

You can find more details on PHP reference count here