In PHP, how do I extract multiple e-mail addresses from a block of text and put them into an array?

I have a block of text from which I want to extract the valid e-mail addresses and put them into an array. So far I have...

   $string = file_get_contents("example.txt"); // Load text file contents
   $matches = array(); //create array
   $pattern = '/[A-Za-z0-9_-]+@[A-Za-z0-9_-]+\.([A-Za-z0-9_-][A-Za-z0-9_]+)/'; //regex for pattern of e-mail address
   preg_match($pattern, $string, $matches); //find matching pattern

However, I am getting an array with only one address. Therefore, I am guessing I need to cycle through this process somehow. How do I do that?

You're pretty close, but the regex wouldn't catch all email formats, and you don't need to specify A-Za-z, you can just use the "i" flag to mark the entire expression as case insensitive. There are email format cases that are missed (especially subdomains), but this catches the ones I tested.

$string = file_get_contents("example.txt"); // Load text file contents

// don't need to preassign $matches, it's created dynamically

// this regex handles more email address formats like [email protected], and the i makes it case insensitive
$pattern = '/[a-z0-9_\-\+]+@[a-z0-9\-]+\.([a-z]{2,3})(?:\.[a-z]{2})?/i';

// preg_match_all returns an associative array
preg_match_all($pattern, $string, $matches);

// the data you want is in $matches[0], dump it with var_export() to see it
var_export($matches[0]);

output:

array (
  0 => '[email protected]',
  1 => '[email protected]',
  2 => '[email protected]',
  3 => '[email protected]',
  4 => '[email protected]',
)

I know this is not the question you asked but I noticed that your regex is not accepting any address like '[email protected]' or any address with a subdomain. You could replace it with something like :

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

which will reject less valid e-mail (although it is not perfect).

I also suggest you read this article on e-mail validation, it is pretty good and informative.