Regex single-line multiple match

Question

With preg_replace in PHP, I am trying to match a regex pattern multiple times in a string, sometimes there will be 2 matches on 1 lines, sometimes not.

I have the following string:

 $text = 'Check <a href="link1">text1</a> or <a href="link2">text2</a>
 oh
 well <a href="link3">text3</a>';

I would like it to convert to:

 Check
 text1
 link1
 or
 text2
 link2
 oh
 well
 text3
 link3

I have this:

 $text = preg_replace('/(<a href=")(.+)(">)(.*)(<\/a>)/', "\n$4\n$2\n", $text);

But it doesn't work, only when having 1 match at a line. Like:

 $text = 'Check <a href="link1">text1</a> 
 or <a href="link2">text2</a>
 oh
 well <a href="link3">text3</a>'; 

Any help appreciated.

Example with a and b http://www.phpliveregex.com/p/4fU

Answer 1

Iterate over all text nodes you can find inside the given HTML and create a special case for parent anchors:

$text = 'Check <a href="link1">text1</a> or <a href="link2">text2</a>
 oh
 well <a href="link3">text3</a>';

$dom = new DOMDocument;
$dom->loadHTML($text);

$xpath = new DOMXPath($dom);

foreach ($xpath->query('//text()') as $node) {
  if ($node->nodeType == XML_TEXT_NODE) {
        echo $node->textContent, "\n";
        if ($node->parentNode->nodeType == XML_ELEMENT_NODE && $node->parentNode->nodeName == 'a') {
                echo $node->parentNode->getAttribute('href'), "\n";
        }
  }
}

In a textual domain, you would do it like this:

echo preg_replace('~<a href="([^"]+)">([^<]+)</a>~i', "\n\$2\n\$1", $text);

Basically you use negative character sets for the href and tag contents enclosure instead of simply .+ and .* because those are greedy by default; this can be changed by using .+? and .*? respectively, but a negative character set would lead to less backtracking.

Also, you only need to perform memory captures on two parts of the anchor, not all five of them.

Answer 2

NOT for your problem but you can add modifiers to a regex pattern after last slash:

preg_replace('/whatever_my_pattern_do/MODIFIERS',"here I replace", $text);

You should check them all here