From the Professional PHP Blog today there are two "preg_replace gotchas" they wanted to let you know about.

preg_replace is a major workhorse function in PHP. Unfortunately, there are some less than obvious issues with using it properly. Here are two:

• The e modifier causes the replacement value of preg_replace (including backreferences) to be evaluated as PHP code. This is a powerful capability. If you've ever seen an SQL injection, this sounds dangerous. It would be, too, but PHP automatically escapes any backreferences because building the string to evaluate.
• Second, most users of the preg_ functions are familiar with preg_quote for escaping strings to use them as literals in regular expression patterns. However, many people don't realize that the replacement parameter of preg_replace also has special characters.

He also gives code examples of each of these situations and shows you what to do to take the safer route around them...

From the Professional PHP Blog today there are two "preg_replace gotchas" they wanted to let you know about.

preg_replace is a major workhorse function in PHP. Unfortunately, there are some less than obvious issues with using it properly. Here are two:

• The e modifier causes the replacement value of preg_replace (including backreferences) to be evaluated as PHP code. This is a powerful capability. If you've ever seen an SQL injection, this sounds dangerous. It would be, too, but PHP automatically escapes any backreferences because building the string to evaluate.
• Second, most users of the preg_ functions are familiar with preg_quote for escaping strings to use them as literals in regular expression patterns. However, many people don't realize that the replacement parameter of preg_replace also has special characters.

He also gives code examples of each of these situations and shows you what to do to take the safer route around them...