Need Help :: What does this stuff mean?

[yakoup46]

<?php

$useragent = $_SERVER['HTTP_USER_AGENT'];

 

if (preg_match('|MSIE ([0-9].[0-9]{1,2})|',$useragent,$matched)) {

    $browser_version=$matched[1];

    $browser = 'IE';

} elseif (preg_match( '|Opera ([0-9].[0-9]{1,2})|',$useragent,$matched)) {

    $browser_version=$matched[1];

    $browser = 'Opera';

} elseif(preg_match('|Firefox/([0-9\.]+)|',$useragent,$matched)) {

        $browser_version=$matched[1];

        $browser = 'Firefox';

} elseif(preg_match('|Safari/([0-9\.]+)|',$useragent,$matched)) {

        $browser_version=$matched[1];

        $browser = 'Safari';

} else {

        // browser not recognized!

    $browser_version = 0;

    $browser= 'other';

}

 

print "Browser: $browser $browser_version";

?>

 

I understand what the script does, I just need to know how any why.

I somewhat understand what is going on, but i am not sure what the [1] means. Or what all the / and +'s means next to like Firefox.

 

Basically I was wondering if anyone could explain to me what the heck is going on with this, and how it works.

[yakoup46]

I am so confused. LOL

 

[nrg_alpha]

When a preg pattern is matched, the entire pattern (which must be all there in the variable in question) is stored into array element[0]. The brackets are captures.. so anything found within the brackets are stored into array element[1].. if there is a second pair of capturing brackets within the same pattern, that gets stored into array element[2], etc..

 

So if you look at the first example:

preg_match('|MSIE ([0-9].[0-9]{1,2})|',$useragent,$matched)

 

If the entire pattern is there, it is stored into $matched[0] (due to the third argument within the preg statement, $matched)... all the numbers (sandwiching a dot match all (which should be escaped if the intent is to look for a literal dot) would be stored into $matches[1].

 

The + is called a quantifier (one or more times). So something like: [0-9]+ means a digit one or more consecutive times.. On a note about the character class, the dots inside those don't need to be escaped.. thus [0-9\.]+ could be simply [0-9.]+

 

And finally, the / simply means looking for just that, a / character.

 

The above was a simplified set of explanations... You can learn about regex in the following links:

 

Resources

Regular-expressions

webtoolscollection

Mastering Regular Expressions

Regular Expressions (Part1) - Basic Syntax

PCRE - PHP Manual

[yakoup46]

That actually helps a lot but what is the purpose of the | |.

[nrg_alpha]

Those are delimiters. In preg statements, the entire pattern has to be contained with those.

Delimiters don't have to be |...| They can be any non-whitespace, non alphanumeric ASCII character other than a backslash. I urge you to have a good read through the links provided, as you will learn a lot about regex within those.