remove_basePath.php

<?php

$code = <<<'CODE'
      protected $baseUrl = '/api/countries';

          $client->request('GET', $this->baseUrl . "kek");

        $client->request('GET', $this->baseUrl.'kek');


CODE;
$re = '/((protected|public)\s+\$baseUrl\s+=\s+\'(?<url>[\/\w+]+)\')/m';

preg_match_all($re, $code, $matches, PREG_SET_ORDER);
// \vardump()
$url = $matches[0]['url']; 

echo preg_replace('/(\$this->baseUrl)/m', $url , $code);

// echo $code;
?>