header() - Inserting a Raw Header Lines

This section describes how to use the header() function to insert a raw HTTP response header line to reset the status line, replace an existing header line, or add a new header line.

When a PHP page is requested, the PHP engine will add some basic header lines in the HTTP response. But if you want to add new header lines or change those inserted by the PHP engine, you can use the header() function. Here are some rules on how to use the header() function:

1. The syntax of header() is:

void header(string $line, bool $replace, int $code)

2. $line specifies a complete header line string like "Content-Type: text/html".

3. $replace specifies a Boolean value controlling whether to replace a previously defined header line of the same identifier or not. If $replace = TRUE, the specified header line will replace any existing header lines with the same identifier. If $replace = FALSE, the specified header line will not replace any existing header lines with the same identifier. If $replace is not provided, PHP will assume $replace = TRUE.

4. $code specifies an integer to be used as the HTTP response status code. If $code is not provided, the PHP engine will decide the status code.

5. header() must be called before any output to the entity body, if the output buffering is turned off.

6. If header() is called to set "Location" header line, the status line will be set to "HTTP/1.0 302".

7. When header() is called multiple times, the status line will be always generated first. Other header lines will be generated in same order as their calling statements.

Here a sample PHP script code segment that generates some header lines using the header() function:

   header("HTTP/1.1 200 OK"); // Reset the status line
   header("Cache-Control: no-cache, must-revalidate");
   header("Expires: Mon, 26 Jul 2017 05:00:00 GMT"); // Past time ok
   header("Content-Type: text/html; charset=utf-8");
   header("Content-Length: 9490");
   header("My-Header: SID=909494909", FALSE); // Allow duplicates
   header("My-Header: UID=Herong", FALSE); // Allow duplicates

Last update: 2019.

Table of Contents

 About This Book

 Introduction and Installation of PHP 7.3

 PHP Script File Syntax

 PHP Data Types and Data Literals

 Variables, References, and Constants

 Expressions, Operations and Type Conversions

 Conditional Statements - "if" and "switch"

 Loop Statements - "while", "for", and "do ... while"

 Function Declaration, Arguments, and Return Values

 Arrays - Ordered Maps

 Introduction of Class and Object

 Integrating PHP with Apache Web Server

 Retrieving Information from HTTP Requests

 Creating and Managing Sessions in PHP Scripts

 Sending and Receiving Cookies in PHP Scripts

Controlling HTTP Response Header Lines in PHP Scripts

 What Is an HTTP Response

 HTTP Response Header Lines

header() - Inserting a Raw Header Lines

 HttpRequestGet.php - Viewing Header Lines

 Response Header Lines of Static Files

 HttpHeaderLines.php - Examples of Inserting Header Lines

 Location: - Forcing the Browser to Redirect to Another URL

 Content-Type: - Generating Non-HTML Response Body

 Content-Disposition: - Sending Files for Downloading

 MySQL Server Connection and Access Functions

 Functions to Manage Directories, Files and Images

 SOAP Extension Function and Calling Web Services

 SOAP Server Functions and Examples

 Localization Overview of Web Applications

 Using Non-ASCII Characters in HTML Documents

 Using Non-ASCII Characters as PHP Script String Literals

 Receiving Non-ASCII Characters from Input Forms

 "mbstring" Extension and Non-ASCII Encoding Management

 Managing Non-ASCII Character Strings with MySQL Servers

 Configuring and Sending out Emails

 Outdated Tutorials


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