3v4l.org

run code in 300+ PHP versions simultaneously
<?php function camelCaseToUnderscore($input) { return strtolower(preg_replace('/(?<!^)[A-Z]/', '_$0', $input)); } echo camelCaseToUnderscore('CamelCaseForTheWin'), "\n"; echo camelCaseToUnderscore('ACar'), "\n"; echo camelCaseToUnderscore('BuyACar'), "\n"; echo camelCaseToUnderscore('XML'), "\n"; echo camelCaseToUnderscore('SimpleXML'), "\n";
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
camel_case_for_the_win a_car buy_a_car x_m_l simple_x_m_l
preferences:
207.12 ms | 404 KiB | 300 Q