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 - 8.1.31, 8.2.0 - 8.2.26, 8.3.0 - 8.3.14, 8.4.1 - 8.4.2
camel_case_for_the_win a_car buy_a_car x_m_l simple_x_m_l
preferences:
83.88 ms | 408 KiB | 5 Q