note 110511 added to function.preg-replace

There seems to be some confusion over how greediness works. For those familiar with Regular Expressions in other languages, particularly Perl: it works like you would expect, and as documented. Greedy by default, un-greedy if you follow a quantifier with a question mark. There is a PHP/PCRE-specific U pattern modifier that flips the greediness, so that quantifiers are by default un-greedy, and become greedy if you follow the quantifier with a question mark: http://www.php.net/manual/en/reference.pcre.pattern.modifiers.php To make things clear, a series of examples: <?php $preview = "a bunch of stuff <code>this that</code> and more stuff <code>with a second code block</code> then extra at the end"; $preview_default = preg_replace('/<code>(.*)<\/code>/is', "<code class=\"prettyprint\">$1</code>", $preview); $preview_manually_ungreedy = preg_replace('/<code>(.*?)<\/code>/is', "<code class=\"prettyprint\">$1</code>", $preview); $preview_U_default = preg_replace('/<code>(.*)<\/code>/isU', "<code class=\"prettyprint\">$1</code>", $preview); $preview_U_manually_greedy = preg_replace('/<code>(.*?)<\/code>/isU', "<code class=\"prettyprint\">$1</code>", $preview); echo "Default, no ?: $preview_default\n"; echo "Default, with ?: $preview_manually_ungreedy\n"; echo "U flag, no ?: $preview_U_default\n"; echo "U flag, with ?: $preview_U_manually_greedy\n"; ?> Results in this: Default, no ?: a bunch of stuff <code class="prettyprint">this that</code> and more stuff <code>with a second code block</code> then extra at the end Default, with ?: a bunch of stuff <code class="prettyprint">this that</code> and more stuff <code class="prettyprint">with a second code block</code> then extra at the end U flag, no ?: a bunch of stuff <code class="prettyprint">this that</code> and more stuff <code class="prettyprint">with a second code block</code> then extra at the end U flag, with ?: a bunch of stuff <code class="prettyprint">this that</code> and more stuff <code>with a second code block</code> then extra at the end As expected: greedy by default, ? inverts it to ungreedy. With the U flag, un-greedy by default, ? makes it greedy. ---- Server IP: 69.147.83.199 Probable Submitter: 75.92.165.78 ---- Manual Page -- http://www.php.net/manual/en/function.preg-replace.php Edit -- https://master.php.net/note/edit/110511 Del: integrated -- https://master.php.net/note/delete/110511/integrated Del: useless -- https://master.php.net/note/delete/110511/useless Del: bad code -- https://master.php.net/note/delete/110511/bad+code Del: spam -- https://master.php.net/note/delete/110511/spam Del: non-english -- https://master.php.net/note/delete/110511/non-english Del: in docs -- https://master.php.net/note/delete/110511/in+docs Del: other reasons-- https://master.php.net/note/delete/110511 Reject -- https://master.php.net/note/reject/110511 Search -- https://master.php.net/manage/user-notes.php