PHP Regular Expressions (. *) and (. *?) Difference

When a regular expression contains a repeating quantifier (such as: *,?, +), the usual behavior is to match as many characters as possible, such as: a (. *) b to match the Aabab string, which matches the entire string, which is called a greedy match.

$str = ' Aabab ';
Preg_match ("/A (. *) b", $str, $matches);
Print_r ($matches);

Array ([0]=>aabab [1]=>[aba])

Sometimes we need a lazy match, which is to match as few characters as possible, and then add a question mark behind the classifier, such as (. *?) Use minimal repetition if the entire match is successful.

$str = ' Aabab ';
Preg_match ("A"/A (. *?) b/", $STR, $matches);
Print_r ($matches);

Array ([0]=>aab [1]=>[a])

Analytical

? involving greedy patterns

When a regular expression contains a qualifier that accepts duplicates, the usual behavior is to match as many characters as possible (subject to the entire expression being matched). Take this expression as an example: A.*b, it will match the longest string that begins with a and ends with a B. If you use it to search for Aabab, it will match the entire string aabab. This is called greedy match.

Sometimes we need a lazy match, which is to match as few characters as possible. The qualifier given above can be converted to lazy match mode, just add a question mark after it. this. * means matching any number of repetitions, but using the least repetition if the whole match succeeds. Now look at the lazy version of the example:

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