A function to output a PHP variable in a `<pre>` with trace info in a data attribute.

pre_log.php

<?php
/**
 * @file A function to output a PHP variable in a `<pre>` with a class and trace info.
 * @author Calvin Juárez <me@calvinjuarez.com>
 * @copyright 2017 Calvin Juárez
 * @license MIT {@link https://spdx.org/licenses/MIT.html MIT License on SPDX.org}
 */

/**
 * An inline <pre> log function that attempts to provide caller file and function information
 *
 * @function pre_log
 *
 * @param {mixed} $subject    The variable to export.
 * @param {array} $meta=[]    (Optional) Any HTML attributes to add to the <pre>.
 * @param {array} $affix=[]   (Optional) Strings to insert in the <pre> before and after the
 *                            $subject.
 * @param {array} $echo=true  (Optional) A boolean indicating whether to echo the result.  Set to
 *                            `false` to return the markup as a string instead.
 * @return {string}  If `$echo` is `false`: The result of `var_export()` wrapped in a nice `<pre>`.
 */
function pre_log($subject, $meta=array(), $affix=array('',''), $echo=true) {
	$attributes = '';
	$classes = '';

	// Get origin information.
	if (! isset($meta['data-origin'])) { // we only need to do any of this if `$meta['origin']` isn't already set (allows user override)
		$origin = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 1)[0]; // get the last 2 backtrace items

		if (isset($trace[$i]['file']))
			$attributes .= ' data-origin="' . basename($origin['file']) . '@ln' . $origin['line'] . '"';
	}

	// Process `$meta`.
	if (! empty($meta)) { // we only need to do any of this if $meta has been specified and isn't `''` or something
		if (is_array($meta)) { // …then we should use attributes
			if (isset($meta['class'])) {
				$classes .= $meta['class']; // merges $meta['class'] with the $classes string (allows for classes & attributes)
				unset($meta['class']); // excludes it from the foreach below
			}
			foreach ($meta as $attribute => $value)
				$attributes .= ' ' . $attribute . '="' . $value . '"';
		} elseif (strval($meta)) // …then we should use classes
			$classes = strval($meta);
		else // $meta is empty or malformed, so we're just gonna ignore it.
			$meta = '';
	}

	// Return a <pre> with a class and with info about where it's coming from.
	if (! empty($classes))    $classes    = ' ' . trim($classes);
	if (! empty($attributes)) $attributes = ' ' . trim($attributes);
	$output = '<pre class="php-log' . $classes . '"' . $attributes . '>' . $affix[0] . htmlentities(var_export($subject, true)) . $affix[1] . '</pre>';

	// Echo or return, depending on the value of the `$echo` flag.
	if ($echo)
		echo $output; // echo if we should
	else
		return $output; // otherwise, give it back as a string
}