Bug #16786: ereg_replace substitution behaving badly

From: tom@scl.co.uk Operating system: Linux 2.2.19 PHP version: 4.2.0 PHP Bug Type: Regexps related Bug description: ereg_replace substitution behaving badly Hi, I have just downloaded PHP4.0.2 and several pieces of code broke because ereg_replace() seemed to be working incorrectly: if for example I did the following: $str = "word1-word2"; $str = ereg_replace("^([^-]*)-(.*)", '\1+\2', $str); it works as expected, ($str == "word1+word2") The problem arises if one of the parenthasized subexpression is empty the \x (where x is the number of the subexpression) in the replace string does not get replaced at all, instead of with the empty string eg: $str = "-word2"; $str = ereg_replace("^([^-]*)-(.*)", '\1+\2', $str); for this example I'd expect the result to be ($str == "+word2") but instead you get ($str == "\1+word2") because \1 is empty. I don't believe that this is meant to happen but if it is how are we meant to deal with such a case? -- Edit bug report at http://bugs.php.net/?id=16786&edit=1 -- Fixed in CVS: http://bugs.php.net/fix.php?id=16786&r=fixedcvs Fixed in release: http://bugs.php.net/fix.php?id=16786&r=alreadyfixed Need backtrace: http://bugs.php.net/fix.php?id=16786&r=needtrace Try newer version: http://bugs.php.net/fix.php?id=16786&r=oldversion Not developer issue: http://bugs.php.net/fix.php?id=16786&r=support Expected behavior: http://bugs.php.net/fix.php?id=16786&r=notwrong Not enough info: http://bugs.php.net/fix.php?id=16786&r=notenoughinfo Submitted twice: http://bugs.php.net/fix.php?id=16786&r=submittedtwice