(PHP 5 >= 5.2.0)
RecursiveRegexIterator::__construct — Creates a new RecursiveRegexIterator.
$iterator
   , string $regex
   [, int $mode = self::MATCH
   [, int $flags = 0
   [, int $preg_flags = 0
  ]]] )Creates a new regular expression iterator.
iteratorThe recursive iterator to apply this regex filter to.
regexThe regular expression to match.
modeOperation mode, see RegexIterator::setMode() for a list of modes.
flagsSpecial flags, see RegexIterator::setFlags() for a list of available flags.
preg_flagsThe regular expression flags. These flags depend on the operation mode parameter:
| operation mode | available flags | 
|---|---|
| RecursiveRegexIterator::ALL_MATCHES | See preg_match_all(). | 
| RecursiveRegexIterator::GET_MATCH | See preg_match(). | 
| RecursiveRegexIterator::MATCH | See preg_match(). | 
| RecursiveRegexIterator::REPLACE | none. | 
| RecursiveRegexIterator::SPLIT | See preg_split(). | 
Example #1 RecursiveRegexIterator::__construct() example
Creates a new RegexIterator that filters all strings that start with 'test'.
<?php
$rArrayIterator = new RecursiveArrayIterator(array('test1', array('tet3', 'test4', 'test5')));
$rRegexIterator = new RecursiveRegexIterator($rArrayIterator, '/^test/',
    RecursiveRegexIterator::ALL_MATCHES);
foreach ($rRegexIterator as $key1 => $value1) {
    if ($rRegexIterator->hasChildren()) {
        // print all children
        echo "Children: ";
        foreach ($rRegexIterator->getChildren() as $key => $value) {
            echo $value . " ";
        }
        echo "\n";
    } else {
        echo "No children\n";
    }
}
?>
The above example will output something similar to:
No children Children: test4 test5