How to Prevent Regex from Modifying HTML Tags During `preg_replace`?

Regex to Avoid Modification of HTML Tags

When performing preg_replace on HTML content, it's essential to ensure that the regular expression doesn't inadvertently modify HTML tags. To achieve this, you can utilize an assertion to exclude matches within HTML tags.

Consider the following scenario: To highlight specific words within an HTML page, you're attempting to wrap them in a tag. However, your current regex, /(, also replaces instances of the word within HTML attributes, such as anchor tag's alt attribute.

To resolve this, you can employ a lookahead assertion that verifies whether the word occurs after a > or before any <. Lookahead assertions allow for variable lengths, making the following regex suitable:

/(asf|foo|barr)(?=[^>]*(<|$))/

This regex ensures that the match occurs after any > or before any <. For a detailed explanation of this assertion syntax, refer to http://www.regular-expressions.info/lookaround.html. By incorporating this assertion into your regex, you can exclude matches within HTML tags and precisely modify the content outside of tags.

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