(PHP 5 >= 5.2.0)
RegexIterator::__construct — Create a new RegexIterator
$iterator
   , string $regex
   [, int $mode = self::MATCH
   [, int $flags = 0
   [, int $preg_flags = 0
  ]]] )Create a new RegexIterator which filters an Iterator using a regular expression.
iteratorThe 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 | 
|---|---|
| RegexIterator::ALL_MATCHES | See preg_match_all(). | 
| RegexIterator::GET_MATCH | See preg_match(). | 
| RegexIterator::MATCH | See preg_match(). | 
| RegexIterator::REPLACE | none. | 
| RegexIterator::SPLIT | See preg_split(). | 
Example #1 RegexIterator::__construct() example
Creates a new RegexIterator that filters all strings that start with 'test'.
<?php
$arrayIterator = new ArrayIterator(array('test 1', 'another test', 'test 123'));
$regexIterator = new RegexIterator($arrayIterator, '/^test/');
foreach ($regexIterator as $value) {
    echo $value . "\n";
}
?>
The above example will output something similar to:
test 1 test 123