Check if a string contains the word word in it (case insensitive). If you have no idea, I guess you could try /word/.

Only match lines with the text start, unless text end appears prior to start. Note: end may or may not be in the string. Match start line_end; and don't match line_end; start

I'd like to know if a text contains words with 4 characters or more which are repeated 3 or more times in the text (anywhere in the text). If so, set one (and only one) backreference for each word.

Replace every . (dot) with a - (hyphen) except when the dot is surrounded by digits. E.g.: .a.b.1.2. should become -a-b-1.2-

Match a string that contains any of the following substrings: http://, www., porn, or credit card. But don't match the text if it contains one of: not allowed, filter, or mirc. Don't use word boundaries (anywhere in the text is fine). If you need help, try reading this.

I'm trying to match bit sequences which are alternating between 1 and 0 and never have more than one 1 or 0 in a row. They can be single digits. Try matching this: 0101010, 1010101010 or 1

Could you help me validate my input and only match positive integers between the range of 0 and 100? There can be several numbers in a string which I would want to retrieve. Try out these example strings: ...

Simple name matching Matches english names only, you may add international characters to list of characters.

improved "Ahmed Z" regexp. PHP date format (and input[type=text] format date too): YYYY-MM-DD. Year between [1900-2099]. No leap year check. Month 02 is limited to 29 days.

youtube id 17 matches

Validates a date with ISO 8601 format. Source: http://www.pelagodesign.com/blog/2009/05/20/iso-8601-date-validation-that-doesnt-suck/

Can grab all kinds of valid twitch URLs.

white space before punctuations, outside script and code tags

This regex fetch only the data between content in curly braces (first occurrence, use preg_match_all in php, for all occurrences). This is useful for bad JSON files with wrong format or text between.

This pattern matches the US Postal Code format and captures the seperate parts; basic and +4.