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<?php function camelCaseToUnderscore($input) { return strtolower(preg_replace('/(?<!^)[A-Z]/', '_$0', $input)); } echo camelCaseToUnderscore('caseStudy'), "\n"; echo camelCaseToUnderscore('News'), "\n"; echo camelCaseToUnderscore('BuyACar'), "\n"; echo camelCaseToUnderscore('XML'), "\n"; echo camelCaseToUnderscore('SimpleXML'), "\n";

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