README.md

This works:

$ php7.4 -S localhost:8080 -dopcache.enable_cli=1 -dopcache.preload=declare_preload.php run.php

declare_pear_error.php

<?php
define('PEAR_ERROR_RETURN',     1);

class PEAR_Error
{
    var $mode                 = PEAR_ERROR_RETURN;
}

declare_preload.php

<?php

const PEAR_ERROR_RETURN = 1;

opcache_compile_file(__DIR__ . '/declare.php');

run.php

<?php

$error = new PEAR_Error();

var_dump($error);