Rule source on GitHub

DowngradeStripTagsCallWithArrayRector

Convert 2nd argument in strip_tags() from array to string

 class SomeClass
 {
     public function run($string)
     {
         // Arrays: change to string
-        strip_tags($string, ['a', 'p']);
+        strip_tags($string, '<' . implode('><', ['a', 'p']) . '>');

         // Variables/consts/properties: if array, change to string
         $tags = ['a', 'p'];
-        strip_tags($string, $tags);
+        strip_tags($string, $tags !== null && is_array($tags) ? '<' . implode('><', $tags) . '>' : $tags);
     }
 }

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\DowngradePhp74\Rector\FuncCall\DowngradeStripTagsCallWithArrayRector;

return RectorConfig::configure()
    ->withRules([
        DowngradeStripTagsCallWithArrayRector::class,
    ]);