What is PHP CLI, and how to run scripts from the command line?

PHP CLI (Command-Line Interface) is a feature of PHP that allows you to run PHP scripts from the command line or terminal. Unlike traditional web-based PHP scripts that run in a web server environment, PHP CLI scripts are executed directly on the server or local machine, making them suitable for a wide range of tasks, including automation, scripting, and system administration.

To run PHP scripts from the command line, follow these steps:

1. Install PHP: Ensure that PHP is installed on your system. You can check if PHP is installed by opening a terminal window and running the following command:

```bash
php -v
```

If PHP is not installed, you can download it from the official PHP website (php.net) or use a package manager like `apt` (for Ubuntu) or `brew` (for macOS).

2. Create a PHP Script: Write your PHP script using a text editor of your choice. Save it with a `.php` extension. For example, you can create a file named `myscript.php`.

3. Run the PHP Script: Open your terminal, navigate to the directory containing your PHP script, and run the script using the `php` command:

```bash
php myscript.php
```

4. Command-Line Arguments: You can pass command-line arguments to your PHP script by adding them after the script name. PHP provides access to command-line arguments through the `$argv` array:

```php
// myscript.php
<?php
echo "Hello, " . $argv[1] . "!\n";
```

Run the script with an argument:

```bash
php myscript.php John
```

This will output: “Hello, John!”

5. STDOUT and STDERR: PHP CLI allows you to send output to the standard output (STDOUT) or standard error (STDERR) streams. You can use functions like `echo` or `print` to display output.

6. Script Execution: PHP CLI scripts can perform various tasks, such as file manipulation, data processing, and interacting with databases, making them versatile tools for automating tasks and running server-side scripts without the need for a web server.

PHP CLI is a valuable tool for developers and system administrators, as it provides a convenient way to execute PHP scripts outside of a web server context, making it suitable for a wide range of tasks and automation processes.