Regex - Ignore some parts of string in match

Question

Here's my string:

address='St Marks Church',notes='The North East\'s premier...'

The regex I'm using to grab the various parts using match_all is

'/(address|notes)='(.+?)'/i'

The results are:

address => St Marks Church
notes => The North East\

How can I get it to ignore the \' character for the notes?

Answer 1

Not sure if you're wrapping your string with heredoc or double quotes, but a less greedy approach:

$str4 = 'address="St Marks Church",notes="The North East\'s premier..."';
preg_match_all('~(address|notes)="([^"]*)"~i',$str4,$matches);
print_r($matches);

Output

Array
(
    [0] => Array
        (
            [0] => address="St Marks Church"
            [1] => notes="The North East's premier..."
        )

    [1] => Array
        (
            [0] => address
            [1] => notes
        )

    [2] => Array
        (
            [0] => St Marks Church
            [1] => The North East's premier...
        )

)

Another method with preg_split:

//split the string at the comma
//assumes no commas in text
$parts = preg_split('!,!', $string);
foreach($parts as $key=>$value){
    //split the values at the = sign
    $parts[$key]=preg_split('!=!',$value);
    foreach($parts[$key] as $k2=>$v2){
        //trim the quotes out and remove the slashes
        $parts[$key][$k2]=stripslashes(trim($v2,"'"));
    }
}

Output looks like:

Array
(
    [0] => Array
        (
            [0] => address
            [1] => St Marks Church
        )

    [1] => Array
        (
            [0] => notes
            [1] => The North East's premier...
        )

)

Super slow old-skool method:

$len = strlen($string);
$key = "";
$value = "";
$store = array();
$pos = 0;
$mode = 'key';
while($pos < $len){
  switch($string[$pos]){
    case $string[$pos]==='=':
        $mode = 'value';
        break;
    case $string[$pos]===",":
        $store[$key]=trim($value,"'");
        $key=$value='';
        $mode = 'key';
        break;
    default:
        $$mode .= $string[$pos];
  }

  $pos++;
}
        $store[$key]=trim($value,"'");

Answer 2

Because you have posted that you are using match_all and the top tags in your profile are php and wordpress, I think it is fair to assume you are using preg_match_all() with php.

The following patterns will match the substrings required to buildyour desired associative array:

Patterns that generate a fullstring match and 1 capture group:

1. /(address|notes)='\K(?:\\\'|[^'])*/ (166 steps, demo link)
   
2. /(address|notes)='\K.*?(?=(?<!\\)')/ (218 steps, demo link)

Patterns that generate 2 capture groups:

3. /(address|notes)='((?:\\\'|[^'])*)/ (168 steps, demo link)
   
4. /(address|notes)='(.*?(?<!\\))'/ (209 steps, demo link)

Code: (Demo)

$string = "address='St Marks Church',notes='The North East\'s premier...'";

preg_match_all(
    "/(address|notes)='\K(?:\\\'|[^'])*/",
    $string,
    $out
);
var_export(array_combine($out[1], $out[0]));

echo "\n---\n";

preg_match_all(
    "/(address|notes)='((?:\\\'|[^'])*)/",
    $string,
    $out,
    PREG_SET_ORDER
);
var_export(array_column($out, 2, 1));

Output:

array (
  'address' => 'St Marks Church',
  'notes' => 'The North East\\\'s premier...',
)
---
array (
  'address' => 'St Marks Church',
  'notes' => 'The North East\\\'s premier...',
)

Patterns #1 and #3 use alternatives to allow non-apostrophe characters or apostrophes not preceded by a backslash.

Patterns #2 and #4 (will require an additional backslash when implemented with php demo) use lookarounds to ensure that apostrophes preceded by a backslash don't end the match.

Some notes:

• Using capture groups, alternatives, and lookarounds often costs pattern efficiency. Limiting the use of these components often improves performance. Using negated character classes with greedy quantifiers often improves performance.

• Using \K (which restarts the fullstring match) is useful when trying to reduce capture groups and it reduces the size of the output array.

Answer 3

You should match up to an end quote that isn't preceded by a backslash thus:

(address|notes)='(.*?)[^\\]'

This [^\\] forces the character immediately preceding the ' character to be anything but a backslash.