How to Exclude Matching Keywords within Specific HTML Tags Using Regular Expressions in PHP?

Matching Keywords Outside HTML Anchor Tags Using Regular Expressions in PHP

Matching keywords in HTML text can be a challenge, especially when it comes to avoiding matches within specific tags like anchor tags (keyword" and "already linked keyword ".

The Solution

The provided PHP code leverages a complex regex to achieve the desired result:

<code class="php">$str = preg_replace('~Moses(?!(?>[^)~i',
                    '<a href="novo-mega-link.php"></a>', $str);</code>

Understanding the Regex

The regex comprises a main expression and a negative lookahead:

• Main Expression: Matches the keyword "Moses".
• Negative Lookahead: Checks whether there is a closing tag ahead without any preceding tag. If true, it indicates that the keyword is within an anchor tag and excludes it from the match.

Explanation

The regex works by first matching the keyword. It then employs a negative lookahead to check for the presence of a closing tag without an intervening tag. If the lookahead succeeds, it means the keyword is enclosed within an anchor element, so the match is discarded. Otherwise, the main expression matches the keyword, and it is replaced with the specified HTML code.

Implementation

The code provided assigns the modified string to the $str variable. The regex can be modified as needed to match different keywords or HTML tags.

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