PHP CookBook

Recipe 20.4 Reading from the Keyboard

20.4.1 Problem

You need to read in some typed user input.

20.4.2 Solution

Use fopen( ) with the special filename php://stdin:

print "Type your message. Type '.' on a line by itself when you're done.\n";

$fh = fopen('php://stdin','r') or die($php_errormsg);
$last_line = false;  $message = '';
while (! $last_line) {
    $next_line = fgets($fp,1024);
    if (".\n" == $next_line) {
      $last_line = true;
    } else {
      $message .= $next_line;
    }
}

print "\nYour message is:\n$message\n";

If the Readline extension is installed, use readline( ):

$last_line = false; $message = '';
while (! $last_line) {
    $next_line = readline();
    if ('.' == $next_line) {
        $last_line = true;
    } else {
        $message .= $next_line."\n";
    }
}

print "\nYour message is:\n$message\n";

20.4.3 Discussion

Once you get a file handle pointing to stdin with fopen( ), you can use all the standard file-reading functions to process input (fread( ), fgets( ), etc.) The solution uses fgets( ), which returns input a line at a time. If you use fread( ), the input still needs to be newline-terminated to make fread( ) return. For example, if you run:

$fh = fopen('php://stdin','r') or die($php_errormsg);
$msg = fread($fh,4);
print "[$msg]";

And type in tomato and then a newline, the output is [toma]. The fread( ) grabs only four characters from stdin, as directed, but still needs the newline as a signal to return from waiting for keyboard input.

The Readline extension provides an interface to the GNU Readline library. The readline( ) function returns a line at a time, without the ending newline. Readline allows Emacs and vi-style line editing by users. You can also use it to keep a history of previously entered commands:

$command_count = 1;
while (true) {
    $line = readline("[$command_count]--> ");
    readline_add_history($line);
    if (is_readable($line)) {
        print "$line is a readable file.\n";
    }
    $command_count++;
}

This example displays a prompt with an incrementing count before each line. Since each line is added to the readline history with readline_add_history( ), pressing the up and down arrows at a prompt scrolls through the previously entered lines.

20.4.4 See Also

Documentation on fopen( ) at http://www.php.net/fopen, fgets( ) at http://www.php.net/fgets, fread( ) at http://www.php.net/fread, and the Readline extension at http://www.php.net/readline; the Readline library at http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html.