PHP / Regex: extract string from string

Question

I just started using PHP and hope someone here can help me with this.

I am trying to extract a string ("myRegion") from another string ("mainString") where my string always starts with "myCountry: " and ends with a semicolon (;) if the main string contains more countries after myCountry OR without anything if the main string does not contain more countries after it.

Examples to show different options for main string:

myCountry: region1, region2
myCountry: region1, region2, region3; otherCountry: region1
otherCountry: region1; myCountry: region1; otherCountry: region1, region2

What I want to extract is always the part in bold.

I was thinking of something like the following but this doesn't look right yet:

$myRegions = strstr($mainString, $myCountry);                   
$myRegions = str_replace($myCountry . ": ", "", $myRegions);
$myRegions = substr($myRegions, 0, strpos($myRegions, ";"));

Many thanks in advance for any help with this, Mike.

FYI: You are not using regular expressions in your example. str_replace does not use REGEX - preg_replace does php.net/manual/en/function.preg-replace.php — Andresch Serj
– Andresch Serj, Commented May 7, 2014 at 10:54
I know, just wanted to mention in case it is a better alternative here. — Mike
– Mike, Commented May 7, 2014 at 10:56

wachme · Accepted Answer · 2014-05-07 10:54:27Z

12

Using regular expression:

preg_match('/myCountry\:\s*([^\;]+)/', $mainString, $out);
$myRegion = $out[1];

answered May 7, 2014 at 10:54

wachme

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3 Comments

Mike Over a year ago

Thanks for this ! One question: if there would be more countries after myCountry will this just go until the first semicolon after myCountry (which is what I need) ?

wachme Over a year ago

Yeah. It just takes everything from myCountry: to the first ;

mickmackusa Oct 8 at 10:26

The colon and semicolon do not require escaping.

Sunchock · Accepted Answer · 2020-06-26 08:32:09Z

5

Since from the comments it seems like you are interested in non-regex solutions and since you are a beginner and interested in learning, here's another possible approach using explode. (Hope this is not uncalled for).

Firstly, recognise that you have definitions seperated by ; since it is:

myCountry: region1, region2, region3 ; otherCountry: region1

So, using explode, you can generate an array of your definitions:

$string = 'otherCountry: region1; myCountry: region1; otherCountry: region2, region3';
$definitions = explode (';', $string);

giving you

array(3) {
  [0]=>
  string(21) "otherCountry: region1"
  [1]=>
  string(19) " myCountry: region1"
  [2]=>
  string(31) " otherCountry: region2, region3"
}

You could now iterate over this array (using foreach) and explode it using : and then explode the second result of that using ,. This way you could build up an associative array holding your Countries with their respective regions.

$result = array();
foreach ($definitions as $countryDefinition) {
  $parts = explode (':', $countryDefinition); // parting at the :
  $country = trim($parts[0]); // look up trim to understand this
  $regions = explode(',', $parts[1]); // exploding by the , to get the regions array
  if(!array_key_exists($country, $result)) { // check if the country is already defined in $result
    $result[$country] = array();
  }
  $result[$country] = array_merge($result[$country], $regions);
}

Just a very simple example to play with.

edited Jun 26, 2020 at 8:32

Sunchock

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answered May 7, 2014 at 11:11

Andresch Serj

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3 Comments

Sunchock Over a year ago

Thank you, I suggested an eddit for your array example because it's a little bit confusing. The array had 3 entries but you write only 2 entries. They match with your first sentence but not with your code part with explode.

Andresch Serj Over a year ago

@Sunchock I didn't see your edit but i think i fixed it?

Sunchock Over a year ago

I didn't see changes array(3) { [0]=> string(19) " myCountry: region1, region2, region3" [1]=> string(31) " otherCountry: region1" } would become array(3) { [0]=> string(19) "otherCountry: region1" [1]=> string(31) " myCountry: region1" [2]=> string(31) " otherCountry: region2, region3" } Because your array match with your first sentence but not with your example using explode

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