Regular expression quantifiers are typically greedy. That is, when faced with a quantifier, the engine matches as much as it can while still satisfying the rest of the pattern. For instance:
preg_match("/(<.*>)/", "do <b>not</b> press the button", $match);
// $match[1] is '<b>not</b>'
The regular expression matches from the first less-than sign to the last greater-than sign. In effect, the .* matches everything after the first less-than sign, and the engine backtracks to make it match less and less until finally there’s a greater-than sign to be matched
Greedy and nongreedy quantifiers in Perl-compatible regular expressions
| Greedy quantifier | Nongreedy quantifier |
|---|---|
| ? | ?? |
| * | *? |
| + | +? |
| {m} | {m}? |
| {m,} | {m,}? |
| {m,n} | {m,n}? |
Here’s how to match a tag using a nongreedy quantifier:
preg_match("/(<.*?>)/", "do <b>not</b> press the button", $match);
// $match[1] is "<b>"