正则表达式-preg_replace字符串

Question

i want to replace a string's non-alphanumeric characters into space.

i used $title= preg_replace("/[^a-zA-Z0-9\\s]/", " ", $title);

so when users inputs

abc!?d$

it will be

abc d

but beacuse user input it to a text-input it goes to "x.php?title=abc!?d$". i want it to go to "x.php?title=abc+d" because i want "abc d", "abc$$$$$$$$$d", "abc__.!d" etc. to go to same url. how can i manage this. thank you.

Answer 1

Basically, what you're saying is that if there are more than one replacable characters next to each other, then you only want to put one space character there. Is that right?

In that case, yes, it's easy: you simply need to add a plus sign after the character class in the regex, like so:

$title = preg_replace("/[^a-zA-Z0-9\s]+/", " ", $title);

The plus sign tells regex to look for one or more match of the preceding item.

Hope that helps.

Answer 2

To get rid off unwanted characters use following code:

$_GET['title'] = 'abc__.!d';

$title = preg_replace('/[^a-zA-Z0-9\s]+/', ' ', $_GET['title']); // "abc d"

Now, just redirect to correct URL (if needed)

if ($_GET['title'] != $title) {
    header('Location: ....');
    die('Redirect to ...URL...');
}

Answer 3

Have you tried the \\W switch for matching non-aplha chars? (In conjunction with the + )

$title= preg_replace(/\W+/g, " ", $title);

(In JavaScript you also need the /g flag as well, not sure if this is true for PHP)

EDIT:

The requirement states that all _ should be eliminated, so the following would work.

(\W|_)+

However, probably best to stipulate the exact chars you want in this instance, rather than trying to build up an exclude list, as my asnwer is starting to do.