<?php
    //use a site with lots of email address on.
    $string = file_get_contents("https://stackoverflow.com/questions/3901070/in-php-how-do-i-extract-multiple-e-mail-addresses-from-a-block-of-text-and-put");

    //initialise an empty array.
    $matches = array();

    //regular expression that matches most email addresses, courtesy of @Eric-Karl.
    $pattern = '/[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+.[A-Za-z]{2,4}/';

    //perform global regular expression match, ie search the entire web page for a particular thing, and store it in the previously initialised array.
    preg_match_all($pattern, $string, $matches);

    //output array of values; remove duplicate email addresses, but maintain incremental key count.
    var_dump(array_values(array_unique($matches[0])));

    //store above in array for upcoming bit.
    $neaterArray = array_values(array_unique($matches[0]));

    //count the amount of variables in the array.
    $count = count($neaterArray);

    //implode array values to string.
    $emailsAsString = implode(", ", $neaterArray);

    //present the string, prepended with the count.
    echo "<h3>$count email addresses in total:</h3> $emailsAsString";

?>

array (size=19)
  0 => string 'apple-touch-icon@2.png' (length=22)
  1 => string 'example@slu.edu' (length=15)
  2 => string 'a+b@google.com.sg' (length=17)
  3 => string 'test1+2@gmail.com' (length=17)
  4 => string 'test-2@yahoo.co.jp' (length=18)
  5 => string 'test@test.com' (length=13)
  6 => string 'test@test.co.uk' (length=15)
  7 => string 'test@google.com.sg' (length=18)
  8 => string 'email@domain.info' (length=17)
  9 => string 'email@domain.inf' (length=16)
  10 => string 'first.lastname@domain.be' (length=24)
  11 => string 'lastname@domain.be' (length=18)
  12 => string 'HIDDENFORLOGICALREASONS@cameranh.rs.gov.br' (length=42)
  13 => string 'HIDDENFORLOGICALREASONS@cameranh.rs.go' (length=38)
  14 => string 'myemail@office21.company.com' (length=28)
  15 => string 'mymail@yahoo.com' (length=16)
  16 => string 'my-e.mail@yahoo.com' (length=19)
  17 => string 'joe@mysite.com' (length=14)
  18 => string 'name@example.com.sv' (length=19)
19 email addresses in total:

apple-touch-icon@2.png, example@slu.edu, a+b@google.com.sg, test1+2@gmail.com, test-2@yahoo.co.jp, test@test.com, test@test.co.uk, test@google.com.sg, email@domain.info, email@domain.inf, first.lastname@domain.be, lastname@domain.be, HIDDENFORLOGICALREASONS@cameranh.rs.gov.br, HIDDENFORLOGICALREASONS@cameranh.rs.go, myemail@office21.company.com, mymail@yahoo.com, my-e.mail@yahoo.com, joe@mysite.com, name@example.com.sv

function file_get_contents_curl($url) {
    $ch = curl_init();

    curl_setopt($ch, CURLOPT_AUTOREFERER, TRUE);
    curl_setopt($ch, CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);

    $data = curl_exec($ch);
    curl_close($ch);

    return $data;
}

/[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+.[A-Za-z]{2,4}/

/[a-z0-9._%+-]+@[a-z0-9.-]+.[a-z]{2,4}/i

var_dump(array_values(array_unique($matches[0])));

$neaterArray = array_values(array_unique($matches[0]));

$neaterArray = (array_values(array_unique($matches[0])));
var_dump($neaterArray);

$pattern = '/[w.%+-]+@(?:[a-zd-]+.)+[a-z]{2,4}/iu';
if (!preg_match_all($pattern, $contents, $emails)) {
    echo '<h3>No emails found</h3>';
} else {
    $unique_emails = array_flip(array_flip($emails[0]));
    $count         = sizeof($unique_emails);
    $email_string  = implode(', ', $unique_emails);
    echo "<h3>$count email addresses in total:</h3> $email_string";
}