Extract keywords/tags from string using Preg_match_all

Question

I have the following code

$str = "keyword keyword 'keyword 1 and keyword 2' another 'one more'".'"another keyword" yes,one,two';

preg_match_all('/"[^"]+"|[^"\' ,]+|\'[^\']+\'/',$str,$matches);

echo "<pre>"; print_r($matches); echo "</pre>";

Where I want it to extract keywords from a string, and keep those wrapped within single or double quotes together, this above code works OK, but it returns the values with the quotes in it. I know I can remove these via str_replace or similar, but I'm really looking for a way to solve this via the preg_match_all function.

Output:

Array
(
    [0] => Array
        (
            [0] => keyword
            [1] => keyword
            [2] => 'keyword 1 and keyword 2'
            [3] => another
            [4] => 'one more'
            [5] => "another keyword"
            [6] => yes
            [7] => one
            [8] => two
        )

)

Also, I think my regex is a little be soppy, so any suggestions for a better would would be good :)

Any suggestions / help would be greatly appreciated.

Answer 1

Take a look at this tokenizeQuote function in the comments to the strtok function.

Edit   You need to modify the function because the original only works with double quotes:

function tokenizeQuoted($string)
{
    for ($tokens=array(), $nextToken=strtok($string, ' '); $nextToken!==false; $nextToken=strtok(' ')) {
        $firstChar = $nextToken{0};
        if ($firstChar === '"' || $firstChar === "'") {
            $nextToken = $nextToken{strlen($nextToken)-1} === $firstChar
                ? substr($nextToken, 1, -1)
                : substr($nextToken, 1) . ' ' . strtok($firstChar);
        }
        $tokens[] = $nextToken;
    }
    return $tokens;
}

---

Edit  Maybe you should just write your own parser:  

$tokens = array();
$buffer = '';
$quote = null;
$len = strlen($str);
for ($i=0; $i<$len; $i++) {
    $char = $str{$i};
    if ($char === '"' || $char === "'") {
        if ($quote === null) {
            if ($buffer !== '') {
                $tokens[] = $buffer;
                $buffer = '';
            }
            $quote = $char;
            continue;
        }
        if ($quote == $char) {
            $tokens[] = $buffer;
            $buffer = '';
            $quote = null;
            continue;
        }
    } else if ($char === ',' || $char === ' ') {
        if ($quote === null) {
            if ($buffer !== '') {
                $tokens[] = $buffer;
                $buffer = '';
            }
            continue;
        }
    }
    $buffer .= $char;
}
if ($buffer !== '') {
    $tokens[] = $buffer;
}

Answer 2

preg_match_all('/"([^"]+)"|[^"\' ,]+|\'([^\']+)\'/',$str,$matches);

and use $matches[1] and $matches[2].

Answer 3

this requires a simple function to get what you want, but it works

preg_match_all('/"([^"]+)"|([^"\' ,]+)|\'([^\']+)\'/',$str,$matches);
function r($str) {
    return str_replace(array('\'','"'), array(''), $str);
}
$a = array_map('r', $matches[0]);
print_r($a);

Answer 4

You've almost got it; you just need to use lookarounds to match the quotes:

'/(?<=\')[^\'\s][^\']*+(?=\')|(?<=")[^"\s][^"]*+(?=")|[^\'",\s]+/'