使用preg_replace()将CamelCase转换为snake_case

Question

我现在有一个方法将我的驼峰案例字符串转换为蛇案例,但它分为三个调用preg_replace():

public function camelToUnderscore($string, $us = "-")
{
    // insert hyphen between any letter and the beginning of a numeric chain
    $string = preg_replace('/([a-z]+)([0-9]+)/i', '$1'.$us.'$2', $string);
    // insert hyphen between any lower-to-upper-case letter chain
    $string = preg_replace('/([a-z]+)([A-Z]+)/', '$1'.$us.'$2', $string);
    // insert hyphen between the end of a numeric chain and the beginning of an alpha chain
    $string = preg_replace('/([0-9]+)([a-z]+)/i', '$1'.$us.'$2', $string);

    // Lowercase
    $string = strtolower($string);

    return $string;
}

我编写了测试来验证其准确性,并且它可以正常使用以下输入数组(array('input' => 'output')):

$test_values = [
    'foo'       => 'foo',
    'fooBar'    => 'foo-bar',
    'foo123'    => 'foo-123',
    '123Foo'    => '123-foo',
    'fooBar123' => 'foo-bar-123',
    'foo123Bar' => 'foo-123-bar',
    '123FooBar' => '123-foo-bar',
];

我想知道是否有办法减少我preg_replace()对单行的调用,这会给我相同的结果.有任何想法吗？

注意:参考这篇文章,我的研究向我展示了一个preg_replace()正则表达式,它几乎得到了我想要的结果,除了它不能foo123用于将其转换为的示例foo-123.

Answer 1

你可以使用lookarounds在一个正则表达式中完成所有这些:

function camelToUnderscore($string, $us = "-") {
    return strtolower(preg_replace(
        '/(?<=\d)(?=[A-Za-z])|(?<=[A-Za-z])(?=\d)|(?<=[a-z])(?=[A-Z])/', $us, $string));
}

RegEx演示

代码演示

RegEx说明:

(?<=\d)(?=[A-Za-z])  # if previous position has a digit and next has a letter
|                    # OR
(?<=[A-Za-z])(?=\d)  # if previous position has a letter and next has a digit
|                    # OR
(?<=[a-z])(?=[A-Z])  # if previous position has a lowercase and next has a uppercase letter