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Q:

nsregularexpression - PHP regular expression with optional underscore and number

Hi everyone,

I have a question regarding regular expressions in PHP. I'm currently working on a project where I need to validate a string that may contain an optional underscore followed by a number. However, I'm not very experienced with regular expressions, so I'm struggling a bit with it.

For example, the string could be "hello_1" or "world", and both should be considered valid. Basically, the underscore and number part should be optional.

I would really appreciate it if someone could help me with a regular expression that accomplishes this. Thank you in advance for your assistance!

All Replies

libby.lindgren

User 2: Hi there! I completely understand your struggle with regular expressions in PHP. It can be a bit daunting, but don't worry, I've got you covered!

In my experience, I've used a slightly different approach to tackle a similar situation. Instead of utilizing the `[\w]` character class, I prefer to use `\w` to match a single word character. Additionally, I make use of the `?` metacharacter to make the underscore and number part optional.

So, the regular expression pattern I suggest is:

php
/^\w+(?:_\d+)?$/


Breaking it down, the `^` symbol denotes the start of the string, `\w+` matches one or more word characters, `(?:_\d+)?` allows for an optional non-capturing group consisting of an underscore followed by one or more digits, and the `$` represents the end of the string.

Feel free to give it a shot and see if it works for your specific case. If you have any questions or run into any issues, feel free to ask! I'm here to assist you.

ryann28

User 1: Hey there! I understand your confusion with regular expressions, but I've got good news for you. I've encountered a similar scenario before and was able to resolve it using a regular expression pattern.

You can try using the following PHP regular expression to validate your string:

php
/^[\w]+(_\d+)?$/


Let me break it down for you. The `^` symbolizes the start of the string, `[\w]+` matches one or more word characters (letters, numbers, or underscores), `(_\d+)?` allows for an optional underscore followed by one or more digits, and the `$` signifies the end of the string.

So, this pattern ensures that the string has at least one word character and allows for an optional underscore followed by digits.

I hope this helps! Give it a try and let me know if you encounter any difficulties.

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