Question

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

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将我的preg_replace()次呼叫减少到单行，这会给我相同的结果。有什么想法吗？

注意：Referring to this post，我的研究向我展示了一个preg_replace()正则表达式，它让我几乎我想要的结果，除了它不能用于{的例子{1}}将其转换为foo123。

Answer 1

您可以使用lookarounds在单个正则表达式中执行所有操作：

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

RegEx Demo

Code Demo

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

Answer 2

根据我之前标记的重复帖子，这是我的两分钱。这里接受的解决方案很棒。我只想尝试用共享内容来解决它：

function camelToUnderscore($string, $us = "-") {
    return strtolower(preg_replace('/(?<!^)[A-Z]+|(?<!^|\d)[\d]+/', $us.'$0', $string));
}

示例：

Array
(
    [0] => foo
    [1] => fooBar
    [2] => foo123
    [3] => 123Foo
    [4] => fooBar123
    [5] => foo123Bar
    [6] => 123FooBar
)

foreach ($arr as $item) {
    echo camelToUnderscore($item);
    echo "\r\n";
}

输出：

foo
foo-bar
foo-123
123-foo
foo-bar-123
foo-123-bar
123-foo-bar

说明：

(?<!^)[A-Z]+      // Match one or more Capital letter not at start of the string
|                 // OR
(?<!^|\d)[\d]+    // Match one or more digit not at start of the string

$us.'$0'          // Substitute the matching pattern(s)

online regex

问题已经解决，所以我不会说我希望它有所帮助，但也许有人会觉得这很有用。

修改

此正则表达式有限制：

foo123bar => foo-123bar fooBARFoo => foo-barfoo

感谢@urban指出。以下是他在此问题上发布的三个解决方案的测试链接：

three solutions demo

Answer 3

来自同事：

$string = preg_replace(array($pattern1, $pattern2), $us.'$1', $string);可能会有效

我的解决方案：

public function camelToUnderscore($string, $us = "-")
{
    $patterns = [
        '/([a-z]+)([0-9]+)/i',
        '/([a-z]+)([A-Z]+)/',
        '/([0-9]+)([a-z]+)/i'
    ];
    $string = preg_replace($patterns, '$1'.$us.'$2', $string);

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

    return $string;
}

使用preg_replace（）将CamelCase转换为snake_case

3 个答案: