71

I know PHP is usually used for web development, where there is no standard input, but PHP claims to be usable as a general-purpose scripting language, if you do follow it's funky web-based conventions. I know that PHP prints to stdout (or whatever you want to call it) with print and echo, which is simple enough, but I'm wondering how a PHP script might get input from stdin (specifically with fgetc(), but any input function is good), or is this even possible?

Chris Lutz
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10 Answers10

93

It is possible to read the stdin by creating a file handle to php://stdin and then read from it with fgets() for a line for example (or, as you already stated, fgetc() for a single character):

<?php
$f = fopen( 'php://stdin', 'r' );

while( $line = fgets( $f ) ) {
  echo $line;
}

fclose( $f );
?>
Dave Jarvis
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Patrick Glandien
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48

Reading from STDIN is recommended way

<?php
while (FALSE !== ($line = fgets(STDIN))) {
   echo $line;
}
?>
anatoly techtonik
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26

To avoid having to mess around with filehandles, use file_get_contents() and php://stdin:

$ echo 'Hello, World!' | php -r 'echo file_get_contents("php://stdin");'
Hello, World!

(If you're reading a truly huge amount of data from stdin you might want to use the filehandle approach, but this should be good for many megabytes.)

mjs
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  • That will block the script and the web server indefinitely! Use `file_get_contents('php://input')` instead, that works. – ygoe Apr 04 '23 at 21:07
17

A simple method is 

$var = trim(fgets(STDIN));
Muhammad Usman
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13

Grab it all in one shot:

$contents = file_get_contents("php://stdin");
echo $contents;
redolent
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  • That will block the script and the web server indefinitely! Use `file_get_contents('php://input')` instead, that works. – ygoe Apr 04 '23 at 21:07
8

You can use fopen() on php://stdin:

$f = fopen('php://stdin', 'r');
Greg
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6

This also works: 

$data = stream_get_contents(STDIN);
Andy
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Richard Cross
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5

When using fgets, it may block in bash scripts, if the stdin isn't set or empty, including while using the @ php error control operator.

#!/usr/bin/php
<?php
$pipe = @trim(fgets(STDIN));
// Script was called with an empty stdin
// Fail to continue, php warning

This behavior can be avoided by setting stream_set_blocking on the php header:

#!/usr/bin/php
<?php
stream_set_blocking(STDIN, false);
$pipe = @trim(fgets(STDIN));
// Script was called with an empty stdin
// No errors or warnings, continue 
echo $pipe . "!";

As example, to be called as follow:

echo "Hello world" | ./myPHPscript
// Output "Hello world!"
./myPHPscript
// Output "!"
NVRM
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    When using the `declare(strict_types=1);` instruction, it is worth noting that setting the second parameter of `stream_set_blocking` to `0` will cause an error as this function expects its second parameter to be a valid boolean value, when providing an integer. Use `stream_set_blocking(STDIN, false);` instead. – Amin NAIRI Aug 07 '19 at 17:42
5

IIRC, you may also use the following:

$in = fopen(STDIN, "r");
$out = fopen(STDOUT, "w");

Technically the same, but a little cleaner syntax-wise.

Fritz H
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1

Instead of manually opening STDIN stream, use built in readline() function if you just want to read a single line without too much a hassle :

<?php
$age= readline("Enter your age: ");
echo "Your age is : ".$age;

PHP documentation is your friend : https://www.php.net/manual/en/function.readline.php

Donovan P
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