替换条件字符串-PHP

Question

i am facing an issue here , trying to replace string with another under a condition. check the example :

$data = '
tony is playing with toys.
tony is playing with "those toys that are not his" ';

so i want to replace toys with cards . but only which is NOT in ques ( " ).

i know how to replace all words that are toys .

$data = str_replace("toys", "cards",$data);

but i don't know how to add a condition which specifies to replace only the one's which are not in the ( " ).

can anyone help please ?

Answer 1

You'll need to parse the string to identify the regions that are not within quotes. You can do this with a state-machine or regular-expression that supports counting.

Here's a pseudocode example:

typedef Pair<int,int> Region;
List<Region> regions;

bool inQuotes = false;
int start = 0;
for(int i=0;i<str.length;i++) {
    char c = str[i];
    if( !inQuotes && c == '"' ) {
        start = i;
        inQuotes = true;
    } else if( inQuotes && c == '"' ) {
        regions.add( new Region( start, i ) );
        inQuotes = false;
    }

}

Then split the string up according to regions , each alternate region will be in quotes.

Challenge for the reader: get it so it handles escaped quotes :)

Answer 2

You could use regex and use a negative lookaround to find the line without the quotes then do a string replace on that.

^((?!\"(.+)?toys(.+)?\").)*

eg

preg_match('/^((?!\"(.+)?toys(.+)?\").)*/', $data, $matches);
$line_to_replace = $matches[0];
$string_with_cards = str_replace("toys", "cards", $line_to_replace);

OR if there are multiple matches you might want to iterate over the array.

http://rubular.com/r/t7epW0Tbqi

Answer 3

Here's one simple way to do it. Split/explode your string using quotation marks. The first ( 0 -index) element and each even-numbered index in the resulting array is unquoted text; the odd numbers are inside quotes. Example:

Test "testing 123" Test etc.
^0    ^1          ^2

Then, just replace the magic words (toys) with the replacement (cards) in only the even-numbered array elements.

Sample code:

function replace_not_quoted($needle, $replace, $haystack) {
    $arydata = explode('"', $haystack);

    $count = count($arydata);
    for($s = 0; $s < $count; $s+=2) {
        $arydata[$s] = preg_replace('~'.preg_quote($needle, '~').'~', $replace, $arydata[$s]);
    }
    return implode($arydata, '"');
}

$data = 'tony is playing with toys.
tony is playing with toys... "those toys that are not his" but they are "nice toys," those toys';

echo replace_not_quoted('toys', 'cards', $data);

So, here, the sample data is:

tony is playing with toys.
tony is playing with toys... "those toys that are not his" but they are "nice toys," those toys

The algorithm works as expected and produces:

tony is playing with cards.
tony is playing with cards... "those toys that are not his" but they are "nice toys," those cards