Regex, or regular expression is used to match characters in a string, the problem with using it is knowing how to use it. As with many things it takes practice and memorization to fully understand and commit it to memory. Regex is a powerful tool and can shorten many tasks such as validating email addresses, redirecting users with mod_rewrite, and searching for illegal characters in a submitted field.
PHP uses two very powerful statements to utilize regex, the first is called preg_match which takes a string and tries to match the pattern you provide it. The second statement is preg_replace which will do the same as preg_match with the exception that it will replace the pattern it finds with some other string you provide. I say only two here and some of you may be thinking “liar!” so I will mention a few others, there is ereg and eregi, they do basically the same things that the preg functions do, just not as fast or powerful. These are the only ones I will be covering, there are several preg functions besides these that you can research at your own pace.
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There comes a time where you feel like shoving your head in a car door and slamming it repeatedly, this is that time. Mod_Rewrite made easy, as easy as it gets I guess, it’s like saying “Learn Quantum Physics in 24 Hours”. Well maybe that is not a fair comparison, either way if you are not familiar with regex and/or you are trying to implement mod_rewrite into an existing site you may need to set plenty of time aside to get it all working correctly.
