wp_debug_backtrace_summary() WP 3.4.0

Return a comma-separated string of functions that have been called to get to the current point in code.

No Hooks.

Return

String/Array. Either a string containing a reversed comma separated trace or an array of individual calls.

Usage

wp_debug_backtrace_summary( $ignore_class, $skip_frames, $pretty );

$ignore_class(string)

A class to ignore all function calls within - useful when you want to just give info about the callee.
Default: null

$skip_frames(int)

A number of stack frames to skip - useful for unwinding back to the source of the issue.
Default: 0

$pretty(true/false)

Whether or not you want a comma separated string or raw array returned.
Default: true

Code of wp debug backtrace summary: wp-includes/functions.php ^{VER 5.1.1}

<?php
function wp_debug_backtrace_summary( $ignore_class = null, $skip_frames = 0, $pretty = true ) {
	static $truncate_paths;

	if ( version_compare( PHP_VERSION, '5.2.5', '>=' ) ) {
		$trace = debug_backtrace( false );
	} else {
		$trace = debug_backtrace();
	}

	$caller      = array();
	$check_class = ! is_null( $ignore_class );
	$skip_frames++; // skip this function

	if ( ! isset( $truncate_paths ) ) {
		$truncate_paths = array(
			wp_normalize_path( WP_CONTENT_DIR ),
			wp_normalize_path( ABSPATH ),
		);
	}

	foreach ( $trace as $call ) {
		if ( $skip_frames > 0 ) {
			$skip_frames--;
		} elseif ( isset( $call['class'] ) ) {
			if ( $check_class && $ignore_class == $call['class'] ) {
				continue; // Filter out calls
			}

			$caller[] = "{$call['class']}{$call['type']}{$call['function']}";
		} else {
			if ( in_array( $call['function'], array( 'do_action', 'apply_filters', 'do_action_ref_array', 'apply_filters_ref_array' ) ) ) {
				$caller[] = "{$call['function']}('{$call['args'][0]}')";
			} elseif ( in_array( $call['function'], array( 'include', 'include_once', 'require', 'require_once' ) ) ) {
				$filename = isset( $call['args'][0] ) ? $call['args'][0] : '';
				$caller[] = $call['function'] . "('" . str_replace( $truncate_paths, '', wp_normalize_path( $filename ) ) . "')";
			} else {
				$caller[] = $call['function'];
			}
		}
	}
	if ( $pretty ) {
		return join( ', ', array_reverse( $caller ) );
	} else {
		return $caller;
	}
}