PHP regular expression: how to match all email links in HTML

Whether it is on a web page or in an email, email links are one of our common elements. In a web page, we may want to match and find all email links at once. At this point, using PHP's regular expressions can conveniently achieve this goal.

PHP is a widely used server scripting language that can be used for tasks such as processing HTML forms, creating dynamic web pages, and interacting with databases. There are many built-in functions in PHP that can easily manipulate strings and regular expressions. Among them, the preg_match_all() function is used to match all substrings that match the given regular expression in a piece of text.

Next, we will explain how to use PHP's preg_match_all() function to match all email links in HTML.

1. Create a regular expression

First, we need to create a regular expression to match all email links. Here, we can consider using a relatively simple regular expression to achieve the goal. For example, we can use the following regular expression to match a standard email link format:

[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+.[A-Z]{2,}

This regular expression can match a letter or number starting with a number, followed by some optional characters (such as dots, underscores, plus sign, minus sign, etc.), followed by an @ symbol and an email domain name. Among them, the domain name consists of letters and numbers, and can have multiple domain name levels, separated by dots. Finally, this regex also requires that the top-level domain name of the domain be two or more uppercase letters. We can save this regular expression into a variable in PHP, for example:

$pattern = '/[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+.[A-Z]{2,}/';

2. Loading HTML file content

Next, we need to load the content from an HTML Read the content from the file and save it to a string variable. In PHP, we can use the file_get_contents() function to read the contents of any network or local file. For example, we can use the following code to read the content from a local file:

$html = file_get_contents('test.html');

3. Match all matching email links

Now, we already have a The regular expression stored in the $pattern variable, and the contents of the HTML file stored in the $html variable. Next, we can use PHP’s preg_match_all() function to match all email links that meet the criteria. This function needs to pass in three parameters: the regular expression to be matched, the text to be matched, and an array to save the matching results.

Here, we can use the following code to achieve the goal:

$matches = array(); 
preg_match_all($pattern, $html, $matches);

In this code, we create an empty array $matches to save the results of regular expression matching . Then, use the preg_match_all() function to match all eligible email links and save the results in the $matches variable.

4. Output matching results

Finally, we can traverse the $matches variable and output all matching email links. For example, we can use the following code to output the matching results:

foreach ($matches[0] as $match) {
    echo $match . "<br/>";
}

In this code, we iterate through the first element of the $matches variable (that is, the array that holds all matching results), and Print the results of each match to the screen.

The complete code is as follows:

$pattern = '/[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+.[A-Z]{2,}/';
$html = file_get_contents('test.html');
$matches = array(); 
preg_match_all($pattern, $html, $matches);

foreach ($matches[0] as $match) {
    echo $match . "<br/>";
}

The above code can match all email links from a file named test.html and output the results to the screen.

Summary:

To match all email links in PHP, you can use the preg_match_all() function and regular expressions. First, we need to create a regular expression to match a standard email link format. Then, we need to use the file_get_contents() function to read the HTML content from a local file or network file and save the content into a string variable. Next, we can use the preg_match_all() function to match all eligible email links and save the results into an array. Finally, we can iterate through each match in the array and print it to the screen.

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