Parsing a string within a string?

Question

I have a function which accepts a string parameter such as: "var1=val1 var2=val2 var3='a list of vals'";

I need to parse this string and pick out the var/val combination's. That is easy enough until introducing something like var3='a list of vals'. Obviously I can't explode the string into an array using a white space delimiter which has me kind of stuck. I want to create an array from this string with the var/val pairs properly assigned, how can I do this in a case where I have something like var3?

Answer 1

Okay, you can't change it. I would use an algorithm like this:

1) Replace all strings contained inside quotes with a unique Id, and store the ID in an array.

So

var1=val1 var2=val2 var3='a list of vals'

becomes

var1=val1 var2=val2 var3=asifab

array("asifab" => 'a list of vals')

2) Split by spaces

array("var1=val1", "var2=val2", "var3=asifab")

array("asifab" => 'a list of vals')

3) split by equal signs

array("var1"=>"val1", "var2"=>"val2", "var3"=>"asifab")

array("asifab" => 'a list of vals')

4) For each value, see if it's in your array, and if it is, split the array value by spaces and use that as the value

array("var1"=>"val1", "var2"=>"val2", "var3"=>array("a", "list", "of", "values"))

Answer 2

Use RegEx with preg_split()?

I'm not great with RE, but I'm sure you can use this to prevent splitting the string inside the single quotes.

Answer 3

if the format of the string is set in stone, you could do something like:

$string = "var1=val1 var2=val2 var3='this is a test'";

$vars = array();
$i = 0;
while ($i < strlen($string)) {

    $eqIndex = strpos($string, "=", $i);
    $varName = substr($string, $i, $eqIndex - $i);

    $i = $eqIndex + 1;

    if ($string[$i] == "'") 
    {
        $varEndIndex = strpos($string, "'", ++$i);
    }
    else
    {
        $varEndIndex = strpos($string, " ", $i);
        if ($varEndIndex === FALSE) $varEndIndex = strlen($string);
    }

    $varValue = substr($string, $i, $varEndIndex - $i);

    $vars[$varName] = $varValue;

    $i = $varEndIndex + 1;
}

print_r($vars);

EDIT:

More robust function that handles escaped chars in the quoted values:

function getVarNameEnd($string, $offset) {

    $len = strlen($string);
    $i = $offset;
    while ($i < $len) {

        if ($string[$i] == "=")
            return $i;
        $i++;
    }

    return $len;
}

function getValueEnd($string, $offset) {

    $len = strlen($string);
    $i = $offset;
    if ($string[$i] == "'") {
        $quotedValue = true;
        $i++;
    }
    while ($i < $len) {

        if ($string[$i] == "\\" && $quotedValue)
            $i++;
        else if ($string[$i] == "'" && $quotedValue)
            return $i + 1;
        else if ($string[$i] == " " && !$quotedValue)
            return $i;
        $i++;
    }

    return $len;
}

function getVars($string) {

    $i = 0;
    $len = strlen($string);
    $vars = array();
    while ($i < $len) {

        $varEndIndex = getVarNameEnd($string, $i);
        $name = substr($string, $i, $varEndIndex - $i);
        $i = $varEndIndex + 1;

        $valEndIndex = getValueEnd($string, $i);
        $value = substr($string, $i, $valEndIndex - $i);
        $i = $valEndIndex + 1;

        $vars[$name] = $value;
    }

    return $vars;
}

$v = getVars("var1=var1 var2='this is a test' var3='this has an escaped \' in it' var4=lastval");
print_r($v);

Answer 4

This is traditionally why query strings use & as the delimiter and not spaces.

If you can do that, then just use parse_str to get the data out.

If not, you'll need to do regex:

preg_match_all('/(\S*)=('.*?'|\S*)/g', $your_string, $matches);
print_r($matches);

Answer 5

You can use a regular expression to find all matching var=val pairs, such as

(\w[0-9A-Za-z]+)=(\'?\w([0-9A-Za-z ]|\\\'|\\=)+\'?)

then you can use preg_match_all to parse them from there, if the string of the second group starts with a ' character you can parse the list.

Answer 6

I'm afraid this problem cannot be solved with simple regex or by simple splitting. Have a look at the str_getcsv() function in PHP 5.3. I think you can make it do exactly what you want.

array str_getcsv  ( string $input  [, string $delimiter  [, string $enclosure  [, string $escape  ]]] )

You can specify delimiter as space instead of comma and enclosure as single quote instead of double quote. If you can, dig up the implementation of this function, understand it, and learn from it. Otherwise get PHP 5.3 to use it.

Edit: There, if you don't have PHP 5.3:

if(!function_exists('str_getcsv')) {
    function str_getcsv($input, $delimiter = ",", $enclosure = '"', $escape = "\\") {
        $fp = fopen("php://memory", 'r+');
        fputs($fp, $input);
        rewind($fp);
        $data = fgetcsv($fp, null, $delimiter, $enclosure); // $escape only got added in 5.3.0
        fclose($fp);
        return $data;
    }
}

Credit: http://www.electrictoolbox.com/php-str-getcsv-function/

Edit: Here's the implementation in Perl: http://search.cpan.org/~makamaka/Text-CSV-1.12/lib/Text/CSV.pm. You can download the source and see the algorithms. If you are up for it :)

Answer 7

Haven't given the whole thing much thought, but what about this? Maybe A LITTLE too much code for such a small task :)

<?php
  function parse_vars($string)
  {
    $exploded = explode(" ", $string);
    $return = array();
    foreach($exploded AS $entry){
      if(strpos($entry, "=") === false){      
        $return[$current] .= " ".$entry;
      }else{
        list($key, $value) = explode("=", $entry);
        $return[$key] = $value;
        $current = $key;
      }
    }   
    return $return;
  }

  $string = "var1=val1 var2=val2 var3='a list of vals'";
  print_r(parse_vars($string));
  die();
?>

By the way I still prefer the regex solution with "(\S*)=('.*?'|\S*)" ...

Answer 8

Perhaps you want the parse_str() function?

Here's the example from PHP.net:

<?php
$str = "first=value&arr[]=foo+bar&arr[]=baz";
parse_str($str);
echo $first;  // value
echo $arr[0]; // foo bar
echo $arr[1]; // baz

parse_str($str, $output);
echo $output['first'];  // value
echo $output['arr'][0]; // foo bar
echo $output['arr'][1]; // baz

?>

It seems to do exactly what you're looking for.