PHP: delete the first line of a text and return the rest

explode() it on the line breaks into an array, shift() off the first line, and rejoin the rest.

$arr = explode("\n", $t);
array_shift($arr);
echo implode("\n", $arr);

// Prints
// All the rest
// Must remain

If your string is really large, this will use a lot of memory. But if your strings are comparable to your example, it will work fine.

Method 2, using strpos()

echo substr($t, strpos($t, "\n") + 1);

How about preg_replace:

$text = "First line.\nSecond line.\nThird line.";
echo preg_replace('/^.+\n/', '', $text);

This way you don't need to worry about the case where there is no newline in your file.
http://codepad.org/fYZuy4LS

In alternative to the other answers with either explode & implode or regular expressions, you can also use strpos() and substr():

function stripFirstLine($text) {        
  return substr($text, strpos($text, "\n") + 1);
}
echo stripFirstLine("First line.\nSecond line.\nThird line.");        

Live example: http://codepad.org/IoonHXE7