PHP Error Handling debug_print_backtrace() Function

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The PHP Error Handling debug_print_backtrace() function is allow you to view the code sequence that leads to an error or a specific program point. The files and functions that were called one after the other are listed in a "backtrace," which is displayed.

This helps developers to identify the potential source of an error. Debugging during development is its primary usage. This feature makes it simpler to find and correct errors in your code.

Syntax

Below is the syntax of the PHP Error Handling debug_print_backtrace() function −

void debug_print_backtrace ( int $options, int $limit )

Parameters

Here are the parameters of the debug_print_backtrace() function −

• $options − (Optional) It is used to specify a bitmask for the following option: DEBUG_IGNORE_BACKTRACE_ARGS (Whether or not to remove all function/method arguments and the "args" index in order to preserve memory.)

• $limit − (Optional) It limits the number of stack frames that can be created. All stack frames are reported by default (limit=0).

Return Value

The debug_print_backtrace() function does not return any value.

PHP Version

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

Example 1

Here is the basic example of the PHP Error Handling debug_print_backtrace() function. The code follows the sequence in which functions are called. When the program runs, the functions one(), two(), and three() are called. Inside three(), debug_print_backtrace() displays the list of these function calls in order.

<?php
   function one() {
      two();
   }

   function two() {
      three();
   }

   function three(){
      debug_print_backtrace();
   }
   one();
?>

Output

Here is the outcome of the following code −

#0 /Users/abc/Desktop/PHP/PhpProjects/index.php(13): three()
#1 /Users/abc/Desktop/PHP/PhpProjects/index.php(9): two()
#2 /Users/abc/Desktop/PHP/PhpProjects/index.php(19): one()

Example 2

In the below PHP code we will use the debug_print_backtrace() function with the $limit parameter. This program limits the number of stack frames in the backtrace to two. This example shows how to limit the amount of functions that are shown in the backtrace with the $limit parameter.

<?php
   function one() {
      two();
   }

   function two() {
      three();
   }

   function three() {
      // Limit backtrace to 2 frames
      debug_print_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT, 2);
   }

   one();
?> 

Output

This will generate the below output −

#0 /Users/abc/Desktop/PHP/PhpProjects/index.php(13): three()
#1 /Users/abc/Desktop/PHP/PhpProjects/index.php(9): two()

Example 3

This program shows how to remove function parameters from the backtrace using the DEBUG_BACKTRACE_IGNORE_ARGS option. In this example, the DEBUG_BACKTRACE_IGNORE_ARGS option is used to hide function parameters in the backtrace.

<?php
   function one($a) {
      two($a, 20);
   }

   function two($b, $c) {
      three($b, $c);
   }

   function three($d, $e) {
      // Ignore function arguments in the backtrace
      debug_print_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
   }

   one(10);
?> 

Output

This will create the below output −

#0 /Users/abc/Desktop/PHP/PhpProjects/index.php(13): three()
#1 /Users/abc/Desktop/PHP/PhpProjects/index.php(9): two()
#2 /Users/abc/Desktop/PHP/PhpProjects/index.php(21): one()

Example 4

In the following example, we will show how to use the debug_print_backtrace() function with class methods and objects. This program tracks the call sequence within a class and object functions to show how debug_print_backtrace() can display the full trace.

<?php
   class Test {
      public function one() {
         $this->two();
      }

      private function two() {
         $this->three();
      }

      protected function three() {
         // Display backtrace with all details
         debug_print_backtrace();
      }
   }

   $obj = new Test();
   $obj->one();
?> 

Output

Following is the output of the above code −

#0 /Users/abc/Desktop/PHP/PhpProjects/index.php(14): Test->three()
#1 /Users/abc/Desktop/PHP/PhpProjects/index.php(10): Test->two()
#2 /Users/abc/Desktop/PHP/PhpProjects/index.php(24): Test->one()