PHP regular greedy way and lazy mode

PHP regular greedy mode and lazy mode
When a regular expression contains a qualifier that can accept duplicates, the usual behavior is to match as many characters as possible (in order for the entire expression to be matched). Consider this expression: A.*b, which will match the longest string starting with a and ending with B. If you use it to search for Aabab, it will match the entire string aabab. This is called a greedy match.

Sometimes we need more lazy matching, which is to match as few characters as possible. The qualifier given above can be converted to lazy matching mode, just add a question mark after it. So. * is meant to match any number of repetitions, but with minimal repetition in the premise that the entire match succeeds. Now look at the lazy version of the example:

A.*?b matches the shortest, starting with a string ending with B. If you apply it to Aabab, it will match AaB (first to third character) and AB (fourth to fifth characters).

Note that if I/I is used in pattern, it is case insensitive
/s represents. Also matches whitespace characters
/U indicates pattern reversal, that is, greedy match mode becomes lazy match mode, lazy match mode becomes greedy match pattern

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