Extracting matches from php regex

Check the php manual

int preg_match ( string $pattern , string $subject [, array &$matches [, int $flags [, int $offset ]]] )

If matches is provided, then it is filled with the results of search. $matches[0] will contain the text that matched the full pattern, $matches1 will have the text that matched the first captured parenthesized subpattern, and so on.

$subject = "E:[email protected] I:100955";
$pattern = "/^E:(?<contact>\w+) I:(?<id>\d+)$/";
if (preg_match($pattern, $subject,$matches)) {
    print_r($matches);
}

The simpler solution

1. go to regex101.com
2. Use the great documentation for creating and testing your regex (make sure you select PHP).

3. In the TOOLS section click on code generation

4. This is an example of what I got.

$re = '/\#.*@hello\((?<operator>\w+),?(?<args>.*)\).*/m';
$str = ' Testing string
# @hello(group_fields)
# @hello(operator, arguments, more arguments)';

preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);

// Print the entire match result
var_dump($matches);

You can just modify your current regexp to capture everything after the colon up to the first space:

$subject = "E:[email protected] I:100955";
$pattern = "/^E:([^ ]+)/";
if (preg_match($pattern, $subject, $m)) {
    echo "Yes, A Match";
}
$email = $m[1];

In case you're not familiar with regexp, [^ ]+ means "any character but a space" and it doesn't require a space to be present to work. If for any reason the input changes to "E:[email protected]" without the " I:12345" bit, it will still work.

Try using the named subpattern syntax of preg_match:

<?php

$str = 'foobar: 2008';

// Works in PHP 5.2.2 and later.
preg_match('/(?<name>\w+): (?<digit>\d+)/', $str, $matches);

// Before PHP 5.2.2, use this:
// preg_match('/(?P<name>\w+): (?P<digit>\d+)/', $str, $matches);

print_r($matches);

?>

Output:

 Array (
     [0] => foobar: 2008
     [name] => foobar
     [1] => foobar
     [digit] => 2008
     [2] => 2008 )