How can I read the contents of stdin (up until EOF) into a string in PHP?

ended up figuring it out myself:

$input_data = file_get_contents("php://stdin");

Use some of the file reading functions (e.g. fgets(), fgetc(), fscanf()) and pass in STDIN as the file path (or php://stdin, depending on how new your version of PHP is).

You can test for the EOF using feof().

See the reference for command-line programming in PHP on PHP.net for more information.