Parsing PHP strings with quoted values

Question

I'd like to parse a string like the following :

'serviceHits."test_server"."http_test.org" 31987'

into an array like :

[0] => serviceHits
[1] => test_server
[2] => http_test.org
[3] => 31987

Basically I want to split in dots and spaces, treating strings within quotes as a single value.

The format of this string is not fixed, this is just one example. It might contain different numbers of elements with quoted and numerical elements in different places.

Other strings might look like :

test.2 3                       which should parse to [test|2|3]
test."342".cake.2 "cheese"     which should parse to [test|342|cake|2|cheese]
test."red feet".3."green" 4    which should parse to [test|red feet|3|green|4]

And sometimes the oid string may contain a quote mark, which should be included if possible, but it's the least important part of the parser:

test."a \"b\" c" "cheese face" which should parse to [test|a "b" c|cheese face]

I'm trying to parse SNMP OID strings from agent written by people with quite varying ideas on what an OID should look like, in a generic manner.

Parsing off the oid string (the bit separated with dots) return value (the last value) into separate named arrays would be nice. Simply splitting on space before parsing the string wouldn't work, as both the OID and the value can contain spaces.

Thanks!

Can you give an few more examples of string you are wanting parsed — Brook Julias
– Brook Julias, Commented Nov 27, 2012 at 1:36
Also a few examples of what you've tried so far. This is a coding request without discernible research effort. — mario
– mario, Commented Nov 27, 2012 at 1:38
Sorry, I assumed no one would want to see my horrific attempts to do it so far. I had pieced together some nasty regexps, but I didn't keep the test files as they didn't work properly! — adama
– adama, Commented Nov 27, 2012 at 22:53
Thanks for adding more examples. Please have a look at my submission below as it passes all your examples and allows escaping of quotes, dots, and spaces. — David Farrell
– David Farrell, Commented Nov 28, 2012 at 7:15

sglessard · Accepted Answer · 2012-11-27 15:33:01Z

3

I agree this can be hard to find one regexp to resolve this issue.

Here's a complete solution :

$results = array();
$str = 'serviceHits."test_\"server"."http_test.org" 31987';

// Encode \" to something else temporary
$str_encoded_quotes = strtr($str,array('\\"'=>'####'));

// Split by strings between double-quotes
$str_arr = preg_split('/("[^"]*")/',$str_encoded_quotes,-1,PREG_SPLIT_DELIM_CAPTURE);

foreach ($str_arr as $substr) {

    // If value is a dot or a space, do nothing
    if (!preg_match('/^[\s\.]$/',$substr)) {

        // If value is between double-quotes, it's a string
        // Return as is
        if (preg_match('/^"(.*)"$/',$substr)) {
            $substr = preg_replace('/^"(.*)"$/','\1',$substr); // Remove double-quotes around
            $results[] = strtr($substr,array('####'=>'"'));    // Get escaped double-quotes back inside the string

        // Else, it must be splitted
        } else {
            // Split by dot or space
            $substr_arr = preg_split('/[\.\s]/',$substr,-1,PREG_SPLIT_NO_EMPTY);
            foreach ($substr_arr as $subsubstr)
                $results[] = strtr($subsubstr,array('####'=>'"')); // Get escaped double-quotes back inside string
        }
    }
    // Else, it's an empty substring
}

var_dump($results);

Tested with all of your new string examples.

First attempt (OLD)

Using preg_split :

$str = 'serviceHits."test_server"."http_test.org" 31987';

// -1 : no limit
// PREG_SPLIT_NO_EMPTY : do not return empty results
preg_split('/[\.\s]?"[\.\s]?/',$str,-1,PREG_SPLIT_NO_EMPTY);

edited Nov 27, 2012 at 15:33

answered Nov 27, 2012 at 1:30

sglessard

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2 Comments

adama Over a year ago

This works well on the example, but not on more complex strings. It doesn't seem to split properly when there is no quotation mark (there isn't always). 'test.45.43.cheese.5 65' poarsed to [0] => test.45.43.cheese.5 65

sglessard Over a year ago

Then add more string examples :)

Cal · Accepted Answer · 2012-11-27 01:52:18Z

2

The easiest way is probably to replace dots and spaces inside strings with placeholders, split, then remove the placeholders. Something like this:

$in = 'serviceHits."test_server"."http_test.org" 31987';

$a = preg_replace_callback('!"([^"]*)"!', 'quote', $in);
$b = preg_split('![. ]!', $a);
foreach ($b as $k => $v) $b[$k] = unquote($v);

print_r($b);


# the functions that do the (un)quoting

function quote($m){
    return str_replace(array('.',' '),
      array('PLACEHOLDER-DOT', 'PLACEHOLDER-SPACE'), $m[1]);
}
function unquote($str){
    return str_replace(array('PLACEHOLDER-DOT', 'PLACEHOLDER-SPACE'),
      array('.',' '), $str);
}

answered Nov 27, 2012 at 1:52

Cal

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1 Comment

adama Over a year ago

This seems to work for all of my examples except the quotes-within-quoted-string one, which isn't overly important. Thanks very much!

David Farrell · Accepted Answer · 2012-11-27 19:21:16Z

Here is a solution that works with all of your test samples (plus one of my own) and allows you to escape quotes, dots, and spaces.

Due to the requirement of handling escape codes, a split is not really possible.

Although one can imagine a regex that matches the entire string with '()' to mark the separate elements, I was unable to get it working using preg_match or preg_match_all.

Instead I parsed the string incrementally, pulling off one element at a time. I then use stripslashes to unescape quotes, spaces, and dots.

<?php

$strings = array
(
    'serviceHits."test_server"."http_test.org" 31987',
    'test.2 3',
    'test."342".cake.2 "cheese"',
    'test."red feet".3."green" 4',
    'test."a \\"b\\" c" "cheese face"',
    'test\\.one."test\\"two".test\\ three',
);

foreach ($strings as $string)
{
    print"'{$string}' => " . print_r(parse_oid($string), true) . "\n";
}

/**
 * parse_oid parses and OID and returns an array of the parsed elements.
 * This is an all-or-none function, and will return NULL if it cannot completely
 * parse the string.
 * @param string $string The OID to parse.
 * @return array|NULL A list of OID elements, or null if error parsing.
 */
function parse_oid($string)
{
    $result = array();
    while (true)
    {
        $matches = array();
        $match_count = preg_match('/^(?:((?:[^\\\\\\. "]|(?:\\\\.))+)|(?:"((?:[^\\\\"]|(?:\\\\.))+)"))((?:[\\. ])|$)/', $string, $matches);
        if (null !== $match_count && $match_count > 0)
        {
            // [1] = unquoted, [2] = quoted
            $value = strlen($matches[1]) > 0 ? $matches[1] : $matches[2];

            $result[] = stripslashes($value);

            // Are we expecting any more parts?
            if (strlen($matches[3]) > 0)
            {
                // I do this (vs keeping track of offset) to use ^ in regex
                $string = substr($string, strlen($matches[0]));
            }
            else
            {
                return $result;
            }
        }
        else
        {
            // All or nothing
            return null;
        }
    } // while
}

This generates the following output:

'serviceHits."test_server"."http_test.org" 31987' => Array
(
    [0] => serviceHits
    [1] => test_server
    [2] => http_test.org
    [3] => 31987
)

'test.2 3' => Array
(
    [0] => test
    [1] => 2
    [2] => 3
)

'test."342".cake.2 "cheese"' => Array
(
    [0] => test
    [1] => 342
    [2] => cake
    [3] => 2
    [4] => cheese
)

'test."red feet".3."green" 4' => Array
(
    [0] => test
    [1] => red feet
    [2] => 3
    [3] => green
    [4] => 4
)

'test."a \"b\" c" "cheese face"' => Array
(
    [0] => test
    [1] => a "b" c
    [2] => cheese face
)

'test\.one."test\"two".test\ three' => Array
(
    [0] => test.one
    [1] => test"two
    [2] => test three
)

Thanks! I'll have to see if this one is better than the one I've already implemented.
Thanks for taking a look - Don't forget to come back and 'Accept' the answer that best matches your original question.
I rewrite our code to incorporate your answer, and it seems to work well. Thanks very much!

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