How to Run a PHP File: Command Line and php -S Server

To run a PHP file, open a terminal in its folder and type php index.php. PHP runs the file and prints its output in the terminal. To see a PHP page in a browser, start the built-in server with php -S localhost:8000 and open http://localhost:8000.

php index.php

A first index.php can be one line. Press Run: this is exactly what php index.php prints.

<?php
echo "Hello from PHP " . PHP_VERSION . "\n";
echo "2 + 3 = " . (2 + 3) . "\n";

PHP code goes after the <?php tag. Anything before that tag is printed as plain text, which is how PHP mixes code with HTML.

Run a PHP file from the command line

The PHP CLI (command line interface) runs a script once and exits. You need PHP installed; if php -v prints an error, see install PHP first.

cd ~/projects/hello
php index.php          # run the file
php -l index.php       # only check the syntax ("lint")
php index.php > out.txt   # save the output to a file

php -l is useful before uploading a file: it reports a parse error with its line number, or No syntax errors detected in index.php.

Pass arguments with $argv

Words after the file name arrive in $argv. $argv[0] is always the script's own name and $argc is the count, including that name. Here the block runs without extra arguments, so only the name is there:

<?php
echo "Script: " . $argv[0] . "\n";
echo "Argument count: " . $argc . "\n";

// Run as: php index.php Ada 3
$name  = $argv[1] ?? 'world';
$times = (int) ($argv[2] ?? 1);

for ($i = 0; $i < $times; $i++) {
    echo "Hello, $name\n";
}

On your own machine, php index.php Ada 3 prints the greeting three times. The ?? fallbacks keep the script working when an argument is missing. For named options like --name=Ada, use getopt:

<?php
// php index.php --name=Ada --verbose
$opts = getopt('', ['name:', 'verbose']);
echo "Hello, " . ($opts['name'] ?? 'world') . "\n";
if (isset($opts['verbose'])) {
    echo "Verbose mode\n";
}

Run PHP in the browser with php -S

PHP has a development web server built in. Start it in the folder with your files:

php -S localhost:8000

[Sat Oct  3 07:21:34 2026] PHP 8.3.19 Development Server (http://localhost:8000) started

Now http://localhost:8000/ runs index.php, and http://localhost:8000/about.php runs about.php. Each page load runs the file again, with the query string in $_GET. The block below behaves the same way: run it, then click a link, and the script runs again with $_GET['page'] set.

<?php
$pages = [
    'home'    => 'Welcome to the bakery.',
    'menu'    => 'Bread, pastries and coffee.',
    'contact' => 'Call us at 555 0100.',
];
$page = $_GET['page'] ?? 'home';
$text = $pages[$page] ?? 'Page not found.';
?>
<nav>
    <a href="?page=home">Home</a> |
    <a href="?page=menu">Menu</a> |
    <a href="?page=contact">Contact</a>
</nav>
<h1><?= htmlspecialchars(ucfirst($page)) ?></h1>
<p><?= htmlspecialchars($text) ?></p>

Useful options:

php -S localhost:8000 -t public        # serve the public/ folder as the web root
php -S 0.0.0.0:8000                    # reachable from other devices on your network
php -S localhost:8000 router.php       # send every request through router.php

The built-in server handles one request at a time and is meant for development only. In production PHP runs behind Nginx or Apache, usually through PHP-FPM.

Check how the script was started

PHP_SAPI tells you which "server API" runs the script: cli in a terminal, cli-server under php -S, and fpm-fcgi or apache2handler behind a real web server. Scripts that should only run from a terminal check it first:

<?php
echo "Running under: " . PHP_SAPI . "\n";
echo "Script name: " . basename(__FILE__) . "\n";

if (PHP_SAPI === 'cli') {
    echo "Command line: plain text output, no HTML needed\n";
} else {
    echo "<p>Web request: send HTML</p>\n";
}

Run a single line with php -r

For a quick test you do not need a file. php -r runs the code you pass, without the <?php tag:

php -r 'echo date("Y-m-d"), PHP_EOL;'
php -r 'var_dump(0.1 + 0.2 == 0.3);'

On Windows cmd, wrap the code in double quotes and use single quotes inside it. For several lines, php -a opens an interactive shell where each statement runs when you press Enter.

Make a script executable on macOS and Linux

Add a shebang line before <?php and mark the file executable. The shebang line is not printed:

#!/usr/bin/env php
<?php
echo "Backup started\n";

chmod +x backup.php
./backup.php

This is how PHP scripts run from cron: 0 3 * * * /usr/bin/php /home/me/backup.php.

Exit codes for scripts

A command-line script reports success or failure through its exit code, which shell scripts and cron can check. exit(0) means success, any other number means failure:

<?php
$file = $argv[1] ?? '';
if (!is_file($file)) {
    fwrite(STDERR, "File not found: $file\n");
    exit(1);
}
echo "Processing $file\n";
exit(0);

Common mistake: running the wrong file or folder

Could not open input file: index.php means PHP cannot find the file from where the terminal is. Check the current folder with pwd (or cd on Windows) and either cd into the project or give the full path: php ~/projects/hello/index.php. With php -S, a 404 for a page you know exists usually means the server was started in a different folder; stop it with Ctrl+C and start it again in the right place, or pass the folder with -t. When the file runs but prints a blank page, turn on error reporting to see what went wrong.