PHP preg_match_all带有“ /”字符的奇怪行为

Question

Using :

preg_match_all(
    "/\b".$KeyWord."\b/u", 
    $SearchStr,
    $Array1,
    PREG_OFFSET_CAPTURE);

This code works fine for all cases except when there is a / in the $KeyWord var. Then I get a warning and unsuccessful match of course.

Any idea how to work around this?

Thanks

Answer 1

use preg_quote() around the keyword.

http://us2.php.net/preg_quote

but also provide your delimiter, so it gets escaped: preg_quote($KeyWord, "/")

Answer 2

您必须解析$ KeyWord并在所有规范符号前添加“ \\”，然后才能使用preg_quote（）

Answer 3

Dynamic Values In Patterns

You are using a dynamic value inside the pattern. Like escaping for SQL or HTML, a specific escaping for the value is needed. If you do not escape meta characters inside the value are interpreted by the regex engine. The escaping function for PCRE patterns is preg_quote() .

preg_match_all(
    "(\b".preg_quote($KeyWord)."\b)u", 
    $SearchStr,
    $Array1,
    PREG_OFFSET_CAPTURE
);

Delimiters

The syntax of a pattern in PHPs preg_* function is:

DELIMITER PATTERN DELIMITER OPTIONS

The / is the delimiter in your pattern. So the / inside the $keyWord was recognized as the closing delimiter.

But all non alphanumeric characters can be used. In Perl and JS you can define a regular expression directly (not as string) using / so it is often the default in tutorials.

Most delimiters have to be escaped inside the pattern.

• Match a \\: '/\\//'

The exception to this rule are brackets. You use any of the bracket pairs as delimiter. And because it is a pair, they can still be used inside the pattern.

• Match a \\: '(/)'

The () brackets are a good decision, you can count them as "subpattern 0".

Answer 4

You can use preg_quote to handle the backslash character.

From the manual:

puts a backslash in front of every character that is part of the regular expression syntax

You can also pass the delimiter as the second parameter and it will also be escaped. However, if you're using # as your delimiter, then there's no need to escape /

So, you can either use:

preg_match_all("/\b".preg_quote($KeyWord, "/")."\b/u", $SearchStr,$Array1,PREG_OFFSET_CAPTURE))

or, if you are sure that your keyword does not contain any other regex-special characters, you can simply change the delimiter, and use to escape the backslash:

preg_match_all("#\b".$KeyWord."\b#u", $SearchStr,$Array1,PREG_OFFSET_CAPTURE))