using Regular Expressions in PHP to return part of a string

Question

I'm trying to retrieve only the version number out of a string, but the strings aren't formatted in a specific. For example, the strings may be written in (but not limited to) any of the following formats

"Angry Birds v2.0.0"
"Angry Birds 2.0.0"
"v1.25"
"Version: 1.3"
" 2.0.1 "

I need to create a php function that will return ONLY the version number (ex: "2.0.0" from each of these strings. Would using regular expressions be useful at all in this task? If so, what built in PCRE (perl compatible regular expressions) PHP functions should I make use of?

Please keep in mind I have very little understanding of regular expressions. Thanks!

Community · Accepted Answer · 2020-06-20 09:12:55Z

3

Try this:

function GetVersion($string)
{
    if (preg_match("#(\d+\.\d+(\.\d+)*)#", $string, $match)) {
        return $match[1];
    }
}

$test_strings = array(
    "Angry Birds v2.0.0",
    "Angry Birds 2.0.0",
    "v1.25",
    "Version: 1.3",
    " 2.0.1 ",
    "Dots4You v3.15"
);

foreach ($test_strings as $string) {
    printf("%s<br>", GetVersion($string));
}

RESULT:

2.0.0

2.0.0

1.25

1.3

2.0.1

3.15

@Tim Pietzcker:

Your code will fail when project's name alone will contain a digit, for example "Dots4You v3.15" will catch "4" as a version. Version should contain at least 2 digits and 1 dot.

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Nov 11, 2011 at 22:36

Czarek Tomczak

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1 Comment

Tim Pietzcker Over a year ago

Your version is a) inelegant (DRY!) and b) also has a bug: Try UltraEdit 17.30.0.1002 (actual version number).

Tim Pietzcker · Accepted Answer · 2011-11-11 22:56:04Z

2

This sounds like a job that regexes are well suited for.

For example:

if (preg_match('/\d+(?:\.\d+)*/', $subject, $regs)) {
    $result = $regs[0];
} else {
    $result = "";
}

Explanation:

\d+  # Match one or more digits
(?:  # Try to match...
 \.  # a dot
 \d+ # and one or more digits...
)*   # zero or more times.

This also matches single version numbers like "Acrobat Reader 9"; if you don't want that and require at least one dot, simply use a + instead of a *: /\d+(?:\.\d+)+/

Or, you could use a word boundary anchor to make sure the regex never matches within a word like "Dots4You": /\d+(?:\.\d+)*\b/

edited Nov 11, 2011 at 22:56

answered Nov 11, 2011 at 22:26

Tim Pietzcker

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4 Comments

user954912 Over a year ago

thank you! Could you explain what '/\d+(?:\.\d+)*/' means? I look at it and I just see gibberish, lol.

Tim Pietzcker Over a year ago

No problem. Check out regular-expressions.info for a great regex tutorial.

Tim Pietzcker Over a year ago

@Czarek: Um, where? Ah, I've seen the comment in your answer. So what about version numbers without a dot in them?

Czarek Tomczak Over a year ago

We could set priority, first try to match version with a dot, then if there are still 2 possible versions with only 1 digit - take the last.

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