Understanding PHP's preg_filter Function

The preg_filter function in PHP is a versatile tool for working with regular expressions. It allows developers to search for and replace text that matches a specific pattern, making it an essential tool for manipulating and cleaning up data.

In this article, we'll dive into the preg_filter function, exploring its syntax, parameters, and use cases. By the end of this article, you'll have a solid understanding of how to use preg_filter in your PHP code.

Syntax and Parameters

The syntax of the preg_filter function is as follows:

preg_filter(pattern, replacement, subject [, limit [, count]])

The parameters are as follows:

  • pattern: This is a regular expression pattern that specifies the text you want to search for.
  • replacement: This is the text that will replace the matching text in the subject.
  • subject: This is the string that you want to search and replace text in.
  • limit (optional): This is the maximum number of replacements that can be made.
  • count (optional): This is a variable that will contain the number of replacements made.

Use Cases

The preg_filter function is useful in a variety of situations where you need to manipulate strings of text. Here are a few common use cases:

  • Removing HTML tags: You can use preg_filter to remove HTML tags from a string, leaving only the text content.
  • Replacing special characters: If you have a string of text with special characters, such as a URL, you can use preg_filter to replace these characters with their encoded equivalents.
  • Formatting data: You can use preg_filter to format data in a specific way, such as converting dates from one format to another.

Example: Removing HTML tags

In this example, we'll use preg_filter to remove HTML tags from a string:


$html = "<p>This is a paragraph.</p>";
$text = preg_filter("/<[^>]+>/", "", $html);
echo $text; // Outputs: "This is a paragraph."


In this example, we're using the regular expression pattern /<[^>]+>/ to match all HTML tags in the $html string. The replacement parameter is set to an empty string, so the matching text is removed. The resulting text is then stored in the $text variable and echoed to the screen.


The preg_filter function in PHP is a powerful tool for working with regular expressions. Whether you're removing HTML tags, replacing special characters, or formatting data, preg_filter makes it easy to manipulate strings of text.

By understanding the syntax, parameters, and use cases of preg_filter, you'll be able to use this function effectively in your own PHP code.

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