Regular expressions: Search a word and append a new word at the end of the line

wordReplaced = wordReplaced.replace(/\[lesserthen\]/g,"<");

re.sub(r'(<form.*?action=")([^"]+)', r'\1newlogin.php',  content)

$subject1 = " [word1 [word1 [word1 [word1 [word3 ";
$pattern1 = preg_quote("[word1 [word1", '/');
$offset=0;
$total=0;
while($count = preg_match("/(?:\s|^|\W)$pattern1(?=\s|$|\W)/", $subject1, $matches, PREG_OFFSET_CAPTURE, $offset)) {
    // summ all matches
    $total  += $count;
    // valorisation of offset with the position of the match + 1
    // the next preg_match will start at this position
    $offset  = $matches[0][1]+1;
}
echo "total=$total\n";

total=3

$pattern = "/[^\\n]*session[^\\n]*/";
// or, with single quotes, you don't need to escape \n
$pattern = '/[^\n]*session[^\n]*/';

$pattern = '/^.*\bsession\b.*$/m';

<?php

$lines ="This is a test
of skipping the word obsessions but
finding the word session in a
bunch of lines of text";

$pattern = "/^.*\bsession\b.*$/m";

$matches = array();
preg_match($pattern, $lines, $matches);

var_dump($matches);

array(1) {
  [0]=>
  string(29) "finding the word session in a"
}

>>> re.findall('[A-Z][A-Za-z]*', text)
['Mitch', 'Pamela']