Headers are the information that is exchanged between client and server for every request and response.
HEADERS in PHP
Headers are of two types.
1. Request Headers.
2. Response Headers.
1) REQUEST HEADERS:-
These are sent from client to server.
HTTP Request : GET/php7/info.php HTTP/1.1
User_Agent : Mozilla/5.0
Accept : text/HTML, application/html
Accept_encoding : gzip,deflate
Connection : keep-alive
keep-alive : 115
Accept_char : ISO-88591-1 utf-8;q=0.7
2) RESPONSE HEADERS:-
These are send from server to client.
X-powered-by : php/5.3.1
keep_Alive : timeout=5,max=100
connection : Keep_Alive
Transfer_Encoding : chunted
content_type : text/html
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Every request from the client to the server can be made through various HTTP methods like
GET, POST, PUT, DELETE, HEAD
Headers can be sent from the PHP program to the server.
1. headers_list():- Returns an array to the list of the headers which can be shared from server to client.
2. headers_sent ():-Returns the boolean value above whether the headers sent to the client or not.
3. header(“:”):-header function should be used on the page before any output is sent to the page.
header functions are used for redirection. header function is used for sending the output of the
PHP content in different formats(content-type like HTML,XHTML,images,pdf,flash,video etc).
The header function is used for downloading the files.
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Uploading and Downloading Files in PHP
The download of a file is done by sending few headers followed by a reading of the source file from the server sending a content-type header
header(“Content-Type:”); pdf -> application/pdf. html -> text/html. jpg/png/gif -> image/(jpg || png || gif).
Step 2: Sending a content Disposition header which will tell the browser to open the file or to ask the user about the file.
Optionally we can send a content-length header with the size of the file.
Reading the Original file: –
readfile()– -> Reads the file Content & prints to the browser..
upload_tmp_dir() -> default is set to c:xampptmp The temporary location to which the file can be uploaded to the server
upload_max_filesize : (<128>) The max size for a single file which can be uploaded to the server -> max_file_uploads : 20..