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Q:

regex php, match string with variable text (letters, numbers, underscore, [])

Hey everyone,

I've been working with regular expressions in PHP, and I'm stuck on a particular task. I need to match a string that can have variable text. Specifically, I want to match strings that contain letters, numbers, underscore, and square brackets [].

For example, I want to match the following strings:
- "abc123"
- "some_text"
- "some[123]text"

But I don't want to match strings like:
- "abc!@#"
- "some*text"

I'm not very experienced with regular expressions, so I would greatly appreciate it if someone could guide me in the right direction. How can I construct a regex pattern that matches the desired strings?

Thanks in advance for your help!

All Replies

boehm.rosina

Hey folks,

I've encountered a similar situation before, and I'd be happy to share my experience with you. When it comes to matching strings with variable text in PHP using regular expressions, there's a neat approach you can take.

To achieve the desired outcome, you can utilize the preg_match function in PHP along with a suitable regular expression pattern. In your case, where you want to match strings containing letters, numbers, underscore, and square brackets [], you can use the following pattern: /[\w\[\]]+/.

Let's break down this pattern for better understanding:
- [\w] matches any word character, which includes letters, numbers, and underscore.
- \[\] matches the square brackets. Similar to the previous response, we need to escape them with a backslash (\) since square brackets have a special meaning in regular expressions.

By appending the + sign at the end, we ensure that the pattern will match one or more characters. If you want to ensure the entire string matches this pattern, you can add the start (^) and end ($) anchors, like this: /^[w\[\]]+$/.

To apply this pattern to your PHP code, consider the following example:

php
$string = "some[123]text";
if (preg_match('/^[\w\[\]]+$/', $string)) {
// The string matches the desired pattern
} else {
// The string doesn't match the desired pattern
}


Feel free to give this approach a shot and let me know if you encounter any further questions. Best of luck with your implementation!

Cheers!

rhowell

Hey there,

I faced a similar situation where I needed to match strings with variable text in PHP using regular expressions. To achieve this, you can use character classes in your regex pattern.

In your case, a character class can be defined using square brackets. Inside the character class, you can list the allowed characters. To match letters, numbers, underscore, and square brackets, the pattern would look like this: /[a-zA-Z0-9_\[\]]+/.

Let me break down this pattern for you:
- [a-zA-Z0-9_] matches any letter (both lowercase and uppercase), any digit, or an underscore.
- \[\] matches square brackets. We need to escape them with a backslash (\) since they have a special meaning in regular expressions.

The + sign at the end allows the pattern to match one or more characters. If you want to ensure the entire string matches this pattern, you can use the start (^) and end ($) anchors like so: /^[a-zA-Z0-9_\[\]]+$/.

You can then use this pattern with PHP's preg_match function to check if a string matches the desired criteria. Here's an example:

php
$string = "some_text";
if (preg_match('/^[a-zA-Z0-9_\[\]]+$/', $string)) {
// The string matches the desired pattern
} else {
// The string doesn't match the desired pattern
}


Feel free to give it a try and let me know if you have any further questions. Good luck with your project!

Cheers!

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