This is a snippet that matches non-alphanumeric characters from a string (text).

<?php
function match_non_alphanumeric_characters($string, $strip_space = true) // Match spaces?
{
$str = ($strip_space) ? ' ' : '';
preg_match_all('/([^a-zA-Z0-9'.$str.']+)/', $string, $match);

return $match[0];
}

$string = 'Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Praesent porttitor euismod enim # Sed posuere & Duis non elit * Sed tempus dolor$';

$non_alphanumeric_array = match_non_alphanumeric_characters($string);

echo '<pre>'; print_r($non_alphanumeric_array); echo "</pre>";
?>

Output:

Array
(
    [0] => ,
    [1] => .
    [2] => #
    [3] => &
    [4] => *
    [5] => $
)

This short snippet is useful if you need to extract alphanumeric sequences (characters) from a string:

function extract_alphanumeric_sequences($string)
{
preg_match_all('/([a-zA-Z0-9]+)/', $string, $match);

return $match[0];
}

$string = 'Suspendisse 354 65pretium eros ut 43564 mauris. Integer in lacus quis est dignissim posuere. Aenean dui.  &$#^@ %$ 94375  Mauris non turpis sit amet nunc imperdiet varius.';

$alpha_array = extract_alphanumeric_sequences($string);

echo '<pre>'; print_r($alpha_array); echo "</pre>";

Output:

Array
(
    [0] => Suspendisse
    [1] => 354
    [2] => 65pretium
    [3] => eros
    [4] => ut
    [5] => 43564
    [6] => mauris
    [7] => Integer
    [8] => in
    [9] => lacus
    [10] => quis
    [11] => est
    [12] => dignissim
    [13] => posuere
    [14] => Aenean
    [15] => dui
    [16] => 94375
    [17] => Mauris
    [18] => non
    [19] => turpis
    [20] => sit
    [21] => amet
    [22] => nunc
    [23] => imperdiet
    [24] => varius
)

This function extracts alphabetical sequences (usually words) from a string (text):

function extract_alphabetical_sequences($string)
{
preg_match_all('/([a-zA-Z]+)/', $string, $match);

return $match[0];
}

$string = 'In hac habitasse platea dictumst. 54 8*5 5#$&*^@  $ @ In eget sem. Etiam quam. Nam nec, justo sed lorem, auctor tincidunt. Nulla id risus laoreet nisl  *^$&&@#$ egestas ultrices.';

$alpha_array = extract_alphabetical_sequences($string);

echo '<pre>'; print_r($alpha_array); echo "</pre>";

Output:

Array
(
    [0] => In
    [1] => hac
    [2] => habitasse
    [3] => platea
    [4] => dictumst
    [5] => In
    [6] => eget
    [7] => sem
    [8] => Etiam
    [9] => quam
    [10] => Nam
    [11] => nec
    [12] => justo
    [13] => sed
    [14] => lorem
    [15] => auctor
    [16] => tincidunt
    [17] => Nulla
    [18] => id
    [19] => risus
    [20] => laoreet
    [21] => nisl
    [22] => egestas
    [23] => ultrices
)

If you need to extract all the words from a string, consider using the str_word_count() function.

This is a short function that extracts numbers from a string:

function extract_numbers($string)
{
preg_match_all('/([\d]+)/', $string, $match);

return $match[0];
}

$string = 'Lorem ipsum dolor sit 45 40 amet, consectetuer adipiscing elit. 35 65675 Suspendisse sed nibh non diam consectetuer pharetra. Morbi ultricies 235 536pede et pede. 9432 3536 Nunc eu risus eget quam lacinia feugiat. In sapien sem, fringilla quis, 34 24 8762condimentum id, bibendum ut, nibh. Quisque 2367 784 elementum massa 350 235 vel nulla.';

$numbers_array = extract_numbers($string);

echo '<pre>'; print_r($numbers_array); echo "</pre>";

Output:

Array
(
    [0] => 45
    [1] => 40
    [2] => 35
    [3] => 65675
    [4] => 235
    [5] => 536
    [6] => 9432
    [7] => 3536
    [8] => 34
    [9] => 24
    [10] => 8762
    [11] => 2367
    [12] => 784
    [13] => 350
    [14] => 235
)