php中preg_match_all()怎么用

preg_match_all(pattern,subject,matches,flags,offset)

";
    var_dump($matches_1);
    var_dump($num_1);
    $pattern_2 = '/(def)(abc)/';
    $num_2 = preg_match_all($pattern_2, $subject, $matches_2,PREG_OFFSET_CAPTURE, 3);
    var_dump($matches_2);
    var_dump($num_2);
?>

array(3) {
  [0]=>array(1) {
    [0]=>string(6) "defabc"
  }
  [1]=>array(1) {
    [0]=>string(3) "def"
  }
  [2]=>array(1) {
    [0]=>string(3) "abc"
  }
}
int(1)
array(3) {
  [0]=>array(1) {
    [0]=>array(2) {
      [0]=>string(6) "defabc"
      [1]=>int(11)
    }
  }
  [1]=>array(1) {
    [0]=>array(2) {
      [0]=>string(3) "def"
      [1]=>int(11)
    }
  }
  [2]=>array(1) {
    [0]=>array(2) {
      [0]=>string(3) "abc"
      [1]=>int(14)
    }
  }
}
int(1)

bold textclick me";
 
preg_match_all("/(<([\w]+)[^>]*>)(.*?)(<\/\\2>)/", $html, $matches, PREG_SET_ORDER);
 
foreach ($matches as $val) {
    echo "matched: " . $val[0] . "\n";
    echo "part 1: " . $val[1] . "\n";
    echo "part 2: " . $val[2] . "\n";
    echo "part 3: " . $val[3] . "\n";
    echo "part 4: " . $val[4] . "\n\n";
}
?>

matched: bold text
part 1: 
part 2: b
part 3: bold text
part 4: 

matched: click me
part 1: 
part 2: a
part 3: click me
part 4: