Custom WordPress Error Handler. Support Query Monitor and can be used as mu-plugin.

snippet.php

<?php
/*
 * Plugin Name: Better errors
 * Description: Better errors in log
 * Author: Daniele Scasciafratte
 * Version: 1.0
 * Author URI: http://codeat.co
*/

function handleError($code, $description, $file = null, $line = null, $context = null) {
    list($error, $log) = mapErrorCode($code);
    $data = array(
        'error' => $error,
        'file' => $file,
        'line' => $line,
        'context' => $context,
        'debug' => var_dump(debug_backtrace()),
        'filter' => current_filter(),
        'message' => $error . ' (' . $code . '): ' . $description
    );
    if(isset($_SERVER['HTTP_HOST'])) {
        $data['url'] = "https://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
    } else {
        $data['cli'] = true;
    }
    return error_log(print_r($data,true));
}

/**
* Map an error code into an Error word, and log location.
*
* @param int $code Error code to map
* @return array Array of error word, and log location.
*/
function mapErrorCode($code) {
    $error = $log = null;
    switch ($code) {
        case E_PARSE:
        case E_ERROR:
        case E_CORE_ERROR:
        case E_COMPILE_ERROR:
        case E_USER_ERROR:
            $error = 'Fatal Error';
            $log = LOG_ERR;
            break;
        case E_WARNING:
        case E_USER_WARNING:
        case E_COMPILE_WARNING:
        case E_RECOVERABLE_ERROR:
            $error = 'Warning';
            $log = LOG_WARNING;
            break;
        case E_NOTICE:
        case E_USER_NOTICE:
            $error = 'Notice';
            $log = LOG_NOTICE;
            break;
        case E_STRICT:
            $error = 'Strict';
            $log = LOG_NOTICE;
            break;
        case E_DEPRECATED:
        case E_USER_DEPRECATED:
            $error = 'Deprecated';
            $log = LOG_NOTICE;
            break;
        default :
            break;
    }
    return array($error, $log);
}

//calling custom error handler
set_error_handler("handleError");

function handleErrorAjax() {
    if ( defined( 'DOING_AJAX' ) ) {
        $type = 'GET';
        if ($_SERVER['REQUEST_METHOD'] === 'POST') {
            $type = 'POST';
        }
        
        error_log("Ajax, " . $type . ": " . print_r(array($_REQUEST),true));
    }
}

if (function_exists('add_action')) {
    add_action('qm/collect/new_php_error', 'handleError', 99999, 5 );
    add_action('init', 'handleErrorAjax', 99999, 5 );
}