PHP Regular Expression: How to match all dropdown menus in HTML

In web development, drop-down menus are a common type of control. In some cases, we need to match all dropdown menu elements in HTML with PHP regular expressions, such as in the case of crawlers or data scraping. This article will show you how to use PHP regular expressions to match all drop-down menus in HTML.

1. First, we need to understand the HTML structure of the drop-down menu control. A drop-down menu usually consists of a select tag and any number of option tags. For example, the HTML structure of a simple drop-down menu looks like this:

<select>
  <option value="1">选项1</option>
  <option value="2">选项2</option>
  <option value="3">选项3</option>
</select>

2. Next, we can use PHP’s regular expression function preg_match_all() to match all drop-down menu elements. The syntax of this function is as follows:

preg_match_all(pattern, subject, matches);

Among them, pattern represents a regular expression, subject is the string to be searched, and matches is the matched result array.

3. For the drop-down menu control, we can use the following regular expression to match its HTML structure:

/<select[^>]*>(.*?)</select>/s

This regular expression can match all select tags, including The option tag. Among them, represents the word boundary, ¹ represents zero or more non-"> " characters, (.?) represents the non-greedy mode Everything, s means let "." match all characters including newlines.

The following is a complete sample code:

$html = '
            选项1
            选项2
            选项3
         
         
            选项4
            选项5
            选项6
         ';

preg_match_all('/<select[^>]*>(.*?)</select>/s', $html, $matches);

print_r($matches);

Run the above code and output the following results:

Array
(
    [0] => Array
        (
            [0] => <select>
            <option value="1">选项1</option>
            <option value="2">选项2</option>
            <option value="3">选项3</option>
         </select>
            [1] => <select>
            <option value="4">选项4</option>
            <option value="5">选项5</option>
            <option value="6">选项6</option>
         </select>
        )

    [1] => Array
        (
            [0] => 
            <option value="1">选项1</option>
            <option value="2">选项2</option>
            <option value="3">选项3</option>
         )
            [1] => 
            <option value="4">选项4</option>
            <option value="5">选项5</option>
            <option value="6">选项6</option>
         )
        )

)

The result array contains two elements, corresponding to two The HTML code for the drop-down menu. If there are more drop-down menus on the page, they will also be matched and saved in the results array.

4. In actual applications, we may also need to use regular expressions to extract the value and text of each option in the drop-down menu. For example, the following code can extract all options from the result array:

foreach ($matches[1] as $select) {
    preg_match_all('/<option value="(.*?)">(.*?)</option>/s', $select, $options);
    print_r($options);
}

The output result is as follows:

Array
(
    [0] => Array
        (
            [0] => <option value="1">选项1</option>
            [1] => <option value="2">选项2</option>
            [2] => <option value="3">选项3</option>
        )

    [1] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
        )

    [2] => Array
        (
            [0] => 选项1
            [1] => 选项2
            [2] => 选项3
        )

)

Note that the "(.*? )" matches the value and text of the option respectively. If you need to extract other attributes, such as the style or ID of the option, you can also add the corresponding pattern in the regular expression.

---

1. > ↩

The above is the detailed content of PHP Regular Expression: How to match all dropdown menus in HTML. For more information, please follow other related articles on the PHP Chinese website!