Input/output streams

The CLI SAPI defines a few constants for I/O streams to make programming for the command line a bit easier.

CLI 专用常量
常量名称 描述
STDIN

An already opened stream to stdin. This saves opening it with

<?php
$stdin = fopen('php://stdin', 'r');
?>
If you want to read single line from stdin, you can use
<?php
$line = trim(fgets(STDIN)); // reads one line from STDIN
fscanf(STDIN, "%d\n", $number); // reads number from STDIN
?>

STDOUT

An already opened stream to stdout. This saves opening it with

<?php
$stdout = fopen('php://stdout', 'w');
?>

STDERR

An already opened stream to stderr. This saves opening it with

<?php
$stderr = fopen('php://stderr', 'w');
?>

有了以上常量，就无需自己建立指向诸如 stderr 的流，只需简单的使用这些常量来代替流指向： 

php -r 'fwrite(STDERR, "stderr\n");'
无需自己来关闭这些流，PHP 会在脚本结束时自动完成这些操作。

Note:

These constants are not available if reading the PHP script from stdin.

User Contributed Notes

phil_php at zieaon dot com 10-Jun-2020 04:42
Under Linux CLI - STDIN, STDOUT and STDERR can be closed and reconnected to a different php stream such as a file, pipe or even a UDP socket_stream. (I use this technique to send the output/errors of my long running background scripts to a file so I can debug if something goes wrong.)

For example: (The below creates/appends file "/tmp/php_stdout.txt")
<?php
// This only works under CLI in Linux
// Note: Until we have closed it STDOUT will NOT be prefixed with a $

// Get the path to the current console for STDOUT so we can reconnect later!
    $strOldSTDOUT=(posix_ttyname(STDOUT)); 

    echo("This will go to the current console\r\n");
// Close the STDOUT resource     
    fclose(STDOUT);   

// Reopen $STDOUT as a file     Note: All further $STDOUT usage will be prefixed with a $
    $STDOUT=fopen("/tmp/php_stdout.txt","a");  /
    echo("This should append the file /tmp/php_stdout.txt\r\n");
// Close stdout again so we can reconnect the console. Note: We are still using
    fclose($STDOUT);   

// Use the path to the console we got earlier   
    $STDOUT=fopen($strOldSTDOUT,"r+");
    echo("And we are back on the console\r\n");

?>
phil_php at zieaon dot com 08-Aug-2018 07:38
The command line interface data in STDIN is not made available until return is pressed.
By adding "readline_callback_handler_install('', function(){});" before reading STDIN for the first time single key presses can be captured.

Note: This only seems to work under Linux CLI and will not work in Apache or Windows CLI.

This cam be used to obscure a password or used with 'stream_select' to make a non blocking keyboard monitor.

<?php

// Demo WITHOUT readline_callback_handler_install('', function(){});
    $resSTDIN=fopen("php://stdin","r");
    echo("Type 'x'. Then press return.");
    $strChar = stream_get_contents($resSTDIN, 1);

    echo("\nYou typed: ".$strChar."\n\n");
    fclose($resSTDIN);
   
// Demo WITH readline_callback_handler_install('', function(){});
// This line removes the wait for <CR> on STDIN
    readline_callback_handler_install('', function(){});
   
    $resSTDIN=fopen("php://stdin","r");
    echo("We have now run: readline_callback_handler_install('', function(){});\n");
    echo("Press the 'y' key");
    $strChar = stream_get_contents($resSTDIN, 1);
    echo("\nYou pressed: ".$strChar."\nBut did not have to press <cr>\n");
    fclose($resSTDIN);
    readline_callback_handler_remove ();
    echo("\nGoodbye\n")
?>

It also hides text from the CLI so can be used for things like. password obscurification.
eg

<?php
    readline_callback_handler_install('', function(){});
    echo("Enter password followed by return. (Do not use a real one!)\n");
    echo("Password: ");
    $strObscured='';
    while(true)
    {
    $strChar = stream_get_contents(STDIN, 1);
    if($strChar===chr(10))
    {
        break;
    }
    $strObscured.=$strChar;
    echo("*");
    }
    echo("\n");
    echo("You entered: ".$strObscured."\n");
?>
ayon at hyurl dot com 21-Feb-2017 12:23
I find a BUG with the constant STDIN, I don't know if it si the Enter/Return key that make this proprem, when I use trim(fgets(STDIN)), that doesn't trim anything, when I detect the length of fgets(STDIN), in windows, it is 2 characters longer than what I input, in Linux, it makes 1. I tried to trim(fgets(STDIN), ' \r\n'), but it still does not work.
So I have to substr the input manually, it seems like this way:
<?php
$STDIN = trim(substr(fgets(STDIN), 0, (PHP_OS == 'WINNT' ? 2 : 1)));
?>
then I get what I want really.
ecrist at secure-computing dot net 27-Jul-2011 08:15
The following code shows how to test for input on STDIN.  In this case, we were looking for CSV data, so we use fgetcsv to read STDIN, if it creates an array, we assume CVS input on STDIN, if no array was created, we assume there's no input from STDIN, and look, later, to an argument with a CSV file name.

Note, without the stream_set_blocking() call, fgetcsv() hangs on STDIN, awaiting input from the user, which isn't useful as we're looking for a piped file. If it isn't here already, it isn't going to be.

<?php
stream_set_blocking(STDIN, 0);
$csv_ar = fgetcsv(STDIN);
if (is_array($csv_ar)){
  print "CVS on STDIN\n";
} else {
  print "Look to ARGV for CSV file name.\n";
}
?>
Aurelien Marchand 04-Mar-2011 08:10
Please remember in multi-process applications (which are best suited under CLI), that I/O operations often will BLOCK signals from being processed.

For instance, if you have a parent waiting on fread(STDIN), it won't handle SIGCHLD, even if you defined a signal handler for it, until after the call to fread has returned.

Your solution in this case is to wait on stream_select() to find out whether reading will block. Waiting on stream_select(), critically, does NOT BLOCK signals from being processed.

Aurelien
James Zhu 09-Dec-2010 01:45
Example:

<?php
function ReadStdin($prompt, $valid_inputs, $default = '') {
    while(!isset($input) || (is_array($valid_inputs) && !in_array($input, $valid_inputs)) || ($valid_inputs == 'is_file' && !is_file($input))) {
        echo $prompt;
        $input = strtolower(trim(fgets(STDIN)));
        if(empty($input) && !empty($default)) {
            $input = $default;
        }
    }
    return $input;
}

// you can input <Enter> or 1, 2, 3
$choice = ReadStdin('Please choose your answer or press Enter to continue: ', array('', '1', '2', '3'));

// check input is valid file name, use /var/path for input nothing
$file = ReadStdin('Please input the file name(/var/path):', 'is_file', '/var/path');
?>

you can add more functions if you want.