PHP CLI vs web server execution

Introduction

PHP can run in two main ways: from the command line or through a web server. Knowing the difference helps you choose the right way to run your PHP code.

You want to run a quick script without opening a browser.

You need to run background tasks or scheduled jobs.

You are building a website that users access through a browser.

You want to test PHP code quickly on your computer.

You want to handle web requests and show web pages.

Syntax

PHP

php script.php  # Run PHP script from command line

// Or access PHP file via web server URL like http://localhost/script.php

PHP CLI means running PHP scripts directly in the terminal or command prompt.

Web server execution means PHP runs when a user visits a web page through a browser.

Examples

This script prints a message when run from the command line.

PHP

<?php
// CLI example
echo "Hello from CLI!\n";

This script shows a message when accessed via a browser.

PHP

<?php
// Web server example
echo "Hello from web server!";

Sample Program

This program detects if PHP is running from the command line or through a web server and prints a message accordingly.

PHP

<?php
if (php_sapi_name() == 'cli') {
    echo "Running in CLI mode\n";
} else {
    echo "Running in web server mode";
}

Important Notes

CLI scripts do not have access to web server variables like $_SERVER['HTTP_HOST'].

Web server execution can handle HTTP requests and send HTML responses.

Use CLI for scripts that do not need a browser, like automation or maintenance tasks.

Summary

PHP CLI runs scripts directly in the terminal without a browser.

Web server execution runs PHP when users visit web pages.

Choose CLI for command-line tasks and web server mode for websites.