PHP中的未知修饰符"/"错误 [英] Unknown modifier '/' error in PHP

问题描述

preg_replace('/http:///ftp:///', 'https://', $value);

$value中的

http://和ftp://应该替换为https://

http:// and ftp:// inside $value should be replaced with https://

此代码给出错误:

preg_replace() [function.preg-replace]: Unknown modifier '/' 

此任务的真正正则表达式是什么?

推荐答案

尝试使用其他定界符，例如#:

Try using a different delimiter, say #:

preg_replace('#http://|ftp://#', 'https://', $value);

或(不建议使用)对正则表达式中每次出现的定界符进行转义:

or (less recommended) escape every occurrence of the delimiter in the regex:

preg_replace('/http:\/\/|ftp:\/\//', 'https://', $value);

另外，您正在搜索模式http:///ftp://，它实际上没有多大意义，也许是您想说的是http://|ftp://.

Also you are searching for the pattern http:///ftp:// which really does not make much sense, may be you meant http://|ftp://.

您可以将正则表达式缩短为:

You can make your regex shorter as:

preg_replace('#(?:http|ftp)#', 'https', $value);

了解错误: Unknown modifier '/'

在正则表达式'/http:///ftp:///'中，第一个/被视为起始定界符，而在:之后的/被视为结束定界符.现在我们知道可以为正则表达式提供修饰符以更改其默认行为.一些这样的修饰符是:

In your regex '/http:///ftp:///', the first / is considered as starting delimiter and the / after the : is considered as the ending delimiter. Now we know we can provide modifier to the regex to alter its default behavior. Some such modifiers are:

• i:匹配大小写 不敏感
• m:多行搜索

• i : to make the matching case insensitive
• m : multi-line searching

但是PHP在结束定界符之后看到的是另一个/，并试图将其解释为修饰符，但失败了，从而导致错误.

But what PHP sees after the closing delimiter is another / and tries to interpret it as a modifier but fails, resulting in the error.

preg_replace返回更改后的字符串.

preg_replace returns the altered string.

$value = 'http://foo.com';
$value = preg_replace('#http://|ftp://#', 'https://', $value);
// $value is now https://foo.com

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