php: how to replace a letter NOT following a backslash

Question

您好，我想将字符串中的所有“ e”替换为“-”而不是反斜杠，因此“ hello”应该是->“ h-llo”，但是“ h \\ ello”应该是“ hello”任何想法一个正则表达式是可能的？

Answer 1

There is no way but to use the e flag if you need to combine both regexes since the replacement is different.

preg_replace('/(\\\\?e)/e', "'\\1'=='e'?'-':'e'", $str);

(Usage: http://www.ideone.com/S2uiS )

There is no need to use regex though. The strtr function is capable of performing this kind of replacement.

strtr($str, array('\\e' => 'e', 'e' => '-'));

(Usage: http://www.ideone.com/yg93g )

Answer 2

您可以在后面使用负号，以确保e之前的字符不是反斜杠：

$string = preg_replace('/(?<!\\)e/', "-", $string);