Instructions for using header, headers_sent, headers_list, header_remove

1.header

void header ( string $string [, bool $replace = true [, int $http_response_code ]] )

Function: Send a customized http message.

Please note that header() must be called before any actual output, whether it is an ordinary html tag, an empty line in a file, a space, or an empty line in a PHP file , space. This is a very common error. When accessing functions in other files through include, require, or other functions, if there are spaces or blank lines before header() is called. If you do not call other files, but just use a PHP or HTML file alone, there will be an error if there is output before header() is called.

Parameter description:

string Message string

replace If true, it means that the next message information of the same type replaces the previous similar message information. The default is true. If set to false, the same message information can be forced to coexist.

http_response_code Forces the value of the HTTP response. Note that this parameter is only valid when the message string (string) is not empty.

Example:Force recharacterization 302 to 303

<?php
header(&#39;location:http://www.example.com/&#39;, true, 303);
?>

2.headers_sent

bool headers_sent ([ string &$file [, int &$line ]] )

Function: Check whether the HTTP header has been sent and where.

Parameter description:

file If this parameter is set, the header will be executed The output PHP source file name is stored in the file variable

line If this parameter is set, the code line number of the PHP source file output by the header will be stored. Enter the line variable

Example:

例子：
<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);
echo &#39;fdipzone<br>&#39;;
ob_end_flush();
if(headers_sent($file, $line)){
    echo "header send in $file on line $line";
}else{
    echo &#39;not header response&#39;;
}
?>

The output of the above example: header send in /home/fdipzone/demo .php on line 5

3.headers_list

array headers_list ( void )

Function:List all The header output (or preparation for output) is returned as an array

Example: Output header list

<?php header(&#39;content-type:text/html;charset=utf-8&#39;);
header(&#39;access-control-allow-origin:*&#39;);
$headers_list = headers_list();
print_r($headers_list);
?>

Output:

Array
(
    [0] => X-Powered-By: PHP/5.4.3
    [1] => content-type:text/html;charset=utf-8
    [2] => access-control-allow-origin:*
)

4.header_remove

void header_remove ([ string $name ] )

Function: Remove a certain header output

Parameter description:

name Header name to be removed

Example:Determine whether there is access-control-allow-origin:*, if so, remove it

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);
header(&#39;access-control-allow-origin:*&#39;);
if(in_array(&#39;access-control-allow-origin:*&#39;, headers_list())){
    header_remove(&#39;access-control-allow-origin&#39;);
}
print_r(headers_list());
?>

This article explains the usage instructions of header, headers_sent, headers_list, header_remove. For more related content, please pay attention to the php Chinese website.

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