Using PHP regex to parse XML

Question

How can I use a regular expression to parse XML?

Let's suppose we have the following:

$string = '<z>1a<z>2b</z>3c<z>4d</z>5e</z>';
preg_match_all('/<z>(.+)<\/z>/', $string, $result_a);
preg_match_all('/<z>(.+)<\/z>/U', $string, $result_b);
preg_match_all($regex, $string, $result_x);

If I run that, then $result_a will have the string (among the items of the array):

'1a<z>2b</z>3c<z>4d</z>5e'

In addition, variable $result_b will have the strings (among the items of the array):

'1a<z>2b'
'4d'

Now, I want $result_x to have '2b' and '4d' separately, among the items of the array.

What should $regex look like?

Thanks in advance!!!

robert · Accepted Answer · 2011-09-16 11:30:43Z

3

In this case you can either use a non-greedy quantifier or you can use this alternative regex:

'/<z>([^<]+)<\/z>/'

[^<] captures all characters except <.

answered Sep 16, 2011 at 11:30

robert

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1 Comment

busce11 Over a year ago

Sorry, I forgot to say it: contents of tags can include < and > characters.

Toto · Accepted Answer · 2011-09-16 14:20:11Z

3

Use non-greedy quantifier:

'/<z>(.+?)<\/z>/'
     ___^

or change the dot by a negative character class:

'/<z>([^z]+)<\/z>/'

or

'/<z>([^<>]+?)<\/z>/'

or, much more convenient, use a xml parser

edited Sep 16, 2011 at 14:20

answered Sep 16, 2011 at 11:23

Toto

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7 Comments

busce11 Over a year ago

Using that regex builds the same result as the second one I described in the example.

busce11 Over a year ago

That's valid, but I would need z to be any kind of XHTML tag. I posted the example using z tag for abstraction purposes, but with z I mean any tag. Using a tag whose name is based on two characters or more with your regex would match in a negative manner the characters that form the name tag, and not the name tag.

Toto Over a year ago

@busce11: So, you have to use a xml parser.

busce11 Over a year ago

I can't use an XML parser. Isn't it possible to modify the second expression you proposed, but instead of saying "one or more characters except for a z" declaring "one or more characters that doesn't include the tag name"?

busce11 Over a year ago

I tried this: '/<z>(?!.*<z>.*)(.+)<\/z>/U' however, it just matched '4d'.

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