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Use \n for CLI scripts on Unix systems; 2. Apply nl2br() for browser line breaks in HTML; 3. Use \r\n for cross-platform file compatibility; 4. Utilize PHP_EOL constant for server-agnostic line endings.

When outputting text in PHP, using the correct line break character is essential for formatting. Here's how to properly use newline characters in different contexts:

The operating environment of this tutorial: MacBook Pro, macOS Sonoma

1. Using \n for Newlines in Command Line Scripts

The \n character is the standard newline in Unix-based systems and works correctly when running PHP scripts via the command line interface (CLI). It tells the terminal to move to the next line.

• Write your PHP script with echo "Line 1\nLine 2";
• Run the script using php filename.php in the terminal
• You will see each string after \n printed on a new line

2. Outputting Line Breaks in Web Browsers with nl2br()

Web browsers do not interpret \n as a visual line break because HTML uses
tags. The nl2br() function converts newline characters into HTML
tags automatically.

• Use echo nl2br("Line 1\nLine 2");
• This outputs Line 1 followed by a
  tag and then Line 2
• The browser renders it as two separate lines

3. Combining \r\n for Cross-Platform Compatibility

Windows systems expect both a carriage return (\r) and line feed (\n), written as \r\n. This combination ensures compatibility across different platforms, especially when generating files or logs.

• Use file_put_contents('log.txt', "Entry 1\r\nEntry 2\r\n", FILE_APPEND);
• This writes each entry on its own line regardless of the server OS
• Helpful when creating downloadable text files from web applications

4. Defining Constants for Environment-Specific Line Endings

PHP provides the built-in constant PHP_EOL which returns the correct end-of-line marker based on the server’s operating system. This is ideal for log files or CLI output where portability matters.

• Use echo "First line" . PHP_EOL . "Second line";
• PHP_EOL returns \n on Linux/macOS and \r\n on Windows
• Ensures consistent behavior when deploying across servers