How to remove HTML tags from string in PHP using regular expressions

In PHP, regular expressions can be used to easily remove HTML tags from strings. HTML tags are usually markup languages ​​enclosed in angle brackets and are used to represent various content in web pages, such as titles, paragraphs, images, links, etc. However, at some point, we may need to remove the HTML tags from the string for better processing and presentation of the data. Let’s take a look at how to use regular expressions to accomplish this task in PHP.

First of all, we need to be clear: using regular expressions to process HTML tags is not a perfect solution. Although regular expressions are very powerful, there are many different forms and uses of HTML tags, so regular expressions may not cover every situation. Therefore, we need to weigh the pros and cons and choose the most appropriate method based on specific needs and data characteristics.

Now, let’s look at some commonly used regular expressions to remove HTML tags from strings.

1. Delete all HTML tags

This method can delete all HTML tags in the string, leaving only plain text content. It uses a very simple regular expression:

$text = preg_replace('/<[^>]*>/', '', $text);

The meaning of this regular expression is: match any string starting with "<" and ending with ">", where ">" precedes "¹" means any character except ">", and "" means it can appear any number of times.

2. Delete specified HTML tags

If you do not want to delete all HTML tags, but only want to delete some specified tags, you can use the following regular expression:

$text = preg_replace('/<(/)?(p|ul|ol|li|strong|em)>/', '', $text);

The meaning of this regular expression is: match strings in the following forms: "

", "

", "

", "

","

", "

", "

", "

", "", "", "" and "". Where "(/)?" represents an optional slash symbol, used to match closing tags such as "/p" and "/ul". "(p|ul|ol|li|strong|em)" represents an optional tag name, where "|" represents a logical OR.

3. Keep the specified HTML tags

Contrary to deleting the specified HTML tags, sometimes we may need to keep some specified tags and delete other tags. At this time, you can use the following regular expression:

$text = preg_replace('/<(?!p|a)(/)?[^>]*>/', '', $text);

The meaning of this regular expression is: match any string starting with "<", where "(?!p|a)" means exclusion All tags except "

" and "". "1*" means any character except ">".

4. Delete HTML tags and their contents

Sometimes, we not only want to delete the HTML tags themselves, but also their contents. At this time, you can use the following regular expression:

$text = preg_replace('/<[^>]*>.*?</[^>]*>/', '', $text);

The meaning of this regular expression is: match anything starting with "<", ending with ">", and containing any characters in the middle until "< A string that appears in combination with ";" and "/". Among them, ".*?" represents any number of arbitrary characters, and "?" represents non-greedy matching to avoid excessive matching.

Summary:

Using regular expressions to process HTML tags can help us quickly delete or retain specified tags. However, it is important to note that regular expressions are not always suitable for all situations. For special needs or special data formats, adjustments and optimizations need to be made according to specific circumstances. To become proficient in regular expressions requires time and energy in learning and practice, but once you master this skill, you can quickly process and display data, improving efficiency and user experience.

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