Split a single string into an array using specific Regex rules

Question

I'm processing a single string which contains many pairs of data. Each pair is separated by a ; sign. Each pair contains a number and a string, separated by an = sign.

I thought it would be easy to process, but i've found that the string half of the pair can contain the = and ; sign, making simple splitting unreliable.

Here is an example of a problematic string:

123=one; two;45=three=four;6=five;

For this to be processed correctly I need to split it up into an array that looks like this:

'123', 'one; two'
'45',  'three=four'
'6',   'five'

I'm at a bit of dead end so any help is appreciated.

UPDATE:

Thanks to everyone for the help, this is where I am so far:

$input = '123=east; 456=west';

// split matches into array
preg_match_all('~(\d+)=(.*?);(?=\s*(?:\d|$))~', $input, $matches);

$newArray = array();

// extract the relevant data
for ($i = 0; $i < count($matches[2]); $i++) {
    $type   = $matches[2][$i];
    $price  = $matches[1][$i];

    // add each key-value pair to the new array
    $newArray[$i] = array(
        'type'      => "$type",
        'price'     => "$price"
    );
}

Which outputs

Array
(
    [0] => Array
        (
            [type] => east
            [price] => 123
        )

)

The second item is missing as it doesn't have a semicolon on the end, i'm not sure how to fix that.

I've now realised that the numeric part of the pair sometimes contains a decimal point, and that the last string pair does not have a semicolon after it. Any hints would be appreciated as i'm not having much luck.

Here is the updated string taking into account the things I missed in my initial question (sorry):

12.30=one; two;45=three=four;600.00=five

Also, if a ; appears in the pair, is it always followed by a space? — Ja͢ck
– Ja͢ck, Commented Apr 19, 2013 at 6:30
I'm using array_combine to sort the array the way I want, which is [123] => one; two; and so on. ; and = in the pair won't always be followed by a space. Thanks. — cianz
– cianz, Commented Apr 19, 2013 at 7:21
Ok i'm not longer using array_combine as it messes up the order of the results. Instead i'm iterating through the matches array and creating a new array with the correct key-value pairs and in the correct order. — cianz
– cianz, Commented Apr 19, 2013 at 8:40

Ja͢ck · Accepted Answer · 2013-04-19 08:55:37Z

1

You need a look-ahead assertion for this; the look-ahead matches if a ; is followed by a digit or the end of your string:

$s = '12.30=one; two;45=three=four;600.00=five';

preg_match_all('/(\d+(?:.\d+)?)=(.+?)(?=(;\d|$))/', $s, $matches);

print_r(array_combine($matches[1], $matches[2]));

Output:

Array
(
    [12.30] => one; two
    [45] => three=four
    [600.00] => five
)

answered Apr 19, 2013 at 8:55

Ja͢ck

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Sergiu Toarca · Accepted Answer · 2013-04-19 05:35:05Z

1

I think this is the regex you want:

\s*(\d+)\s*=(.*?);(?=\s*(?:\d|$))

The trick is to consider only the semicolon that's followed by a digit as the end of a match. That's what the lookahead at the end is for.

You can see a detailed visualization on www.debuggex.com.

answered Apr 19, 2013 at 5:35

Sergiu Toarca

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1 Comment

cianz Over a year ago

Thanks, that works well, although i've now realised that the numeric part of the pair sometimes contains a decimal point, and that the last string pair does not have a semicolon after it. Any hints would be appreciated, i'm playing around in RegexBuddy but not getting very far. Cheers.

anubhava · Accepted Answer · 2013-04-19 05:49:01Z

1

You can use following preg_match_all code to capture that:

$str = '123=one; two;45=three=four;6=five;';
if (preg_match_all('~(\d+)=(.+?);(?=\d|$)~', $str, $arr))
   print_r($arr);

Live Demo: http://ideone.com/MG3BaO

answered Apr 19, 2013 at 5:49

anubhava

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Angelin Nadar · Accepted Answer · 2013-04-19 06:26:29Z

1

$str = '123=one; two;45=three=four;6=five;';

preg_match_all('/(\d+)=([a-zA-z ;=]+)/', $str,$matches);
echo '<pre>';
print_r($matches);
echo '</pre>';

o/p:

Array
(
    [0] => Array
        (
            [0] => 123=one; two;
            [1] => 45=three=four;
            [2] => 6=five;
        )

    [1] => Array
        (
            [0] => 123
            [1] => 45
            [2] => 6
        )

    [2] => Array
        (
            [0] => one; two;
            [1] => three=four;
            [2] => five;
        )

)

then y can combine

echo '<pre>';
print_r(array_combine($matches[1],$matches[2]));
echo '</pre>';

o/p:

Array
(
    [123] => one; two;
    [45] => three=four;
    [6] => five;
)

edited Apr 19, 2013 at 6:26

answered Apr 19, 2013 at 6:19

Angelin Nadar

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CodeNinja · Accepted Answer · 2013-04-19 05:43:15Z

0

Try this but this code is written in c#, you can change it into php

 string[] res = Regex.Split("123=one; two;45=three=four;6=five;", @";(?=\d)");

--SJ

answered Apr 19, 2013 at 5:43

CodeNinja

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