1. PHP – Digging Deeper
Martin Kruliš
by Martin Kruliš (v1.2)

2. HTTP Wrapper - Revision
HTTP Request Wrapper
Data are automatically prepared in superglobal arrays
$_GET – parameters from request URL
$_POST – parameters posted in HTTP body (form data)
$_FILES – records about uploaded files
$_SERVER – server settings and request headers
$_ENV – environment variables
HTTP Response
Script output is the response (echo …)
Headers can be modified by functions – e.g., header('header-line');
by Martin Kruliš (v1.2)

3. HTTP Wrapper - Revision
Example
<form action="?op=update&id=42" method="POST"> <input name="name" type="text"> <input name="surname" type="text"> <input name="age" type="number"> <input type="submit" value="Save"> </form>
'op' => 'update'
'id' => '42'
'name' => 'Martin'
'surname' => 'Kruliš'
'age' => '19'
$_GET
$_POST
Note the & entity used in URL, since it is being included in HTML attribute. Furthermore, note that all values are strings (despite the fact that some of them contain numbers).
Example 1
by Martin Kruliš (v1.2)

4. HTTP Wrapper Request Information Decoded to the $_SERVER array
REQUEST_METHOD – used method (“GET”or “POST”)
SERVER_PROTOCOL – protocol version (“HTTP/1.1”)
REQUEST_URI – request part of URL (“/index.php”)
REMOTE_ADDR – clients IP address
HTTP_ACCEPT – MIME types that the client accepts
HTTP_ACCEPT_LANGUAGE – desired translation
HTTP_ACCEPT_ENCODING – desired encodings
HTTP_ACCEPT_CHARSET – desired charsets
+ more info about the server and the client’s browser
phpinfo()
by Martin Kruliš (v1.2)

5. HTTP Wrapper File Uploads
In form as <input type="file" name=... />
Provide safe way to browse disk files
HTTP wrapper handles the file
Stores it in temporary location
Provide related info in $_FILES[name]
'tmp_name' – path to the file in temp directory
'error' – error code (e.g., UPLOAD_ERR_OK)
'name', 'type', 'size', …
File exists only as long as the script runs
is_uploaded_file() – verification
move_uploaded_file() – a safe way to move files
Let us emphasize that the form must use “multipart/form-data” encoding to successfully handle file uploads.
Example 2
by Martin Kruliš (v1.2)

6. POST Request (a submitted form)
HTTP Issues
Problem with POST
POST Request (a submitted form)
script
add/change
something
Web Server
Refresh
Again!!!
Client (Browser)
Response
(a HTML page)
by Martin Kruliš (v1.2)

7. HTTP Issues Redirect Mechanism in HTTP Creating Redirect in PHP
3xx response code
301 Moved Permanently
302 Found (originally named Moved Temporarily)
303 See Other
Additional header 'Location' has the new URL
Browser must try to load the new URL
Loops in redirections are detected
Creating Redirect in PHP
header("Location: my-new-url");
Automatically changes the response code (to 302)
by Martin Kruliš (v1.2)

8. HTTP Issues Redirect (303 See Other) after POST
POST Request (action.php)
action.php
add/change
something
Redirect (to index.php)
Web Server
Redirects to a new URL (without updating history)
Client (Browser)
index.php generate HTML (only reads DB)
Note that setting Location header in PHP always sets the 302 (Found) response code. This is no big deal; however, it is not entirely correct HTTP semantics.
GET (index.php)
Refresh
HTML Page
Example 3
by Martin Kruliš (v1.2)

9. Redirect and AJAX Redirecting Asynchronous HTTP Requests
Works transparently – i.e., in the same way as all HTTP requests handled by the browser
Typically unnecessary after POST requests
A script should not be re-executed after reload, thus it can receive the updated HTML immediately
Uncertain semantics
Is the redirect meant for the AJAX result or should the whole page load a new URL?
Efficiency
AJAX typically optimizes network utilization – additional redirect may be suboptimal
by Martin Kruliš (v1.2)

10. Redirect and AJAX Example – Replacing Redirect with AJAX
Let us have a data table, where each item has a delete button that triggers AJAX POST request
Trivial solution
After successful request, JS triggers reload of the page
Optionally the req. may send an URL (for location.href)
Slightly more optimized solution
After successful request, JS triggers reload of affected components (table) via separate AJAX GET request
Optimized solution
The POST response sends a HTML fragment or (better yet) a difference update for the data table
by Martin Kruliš (v1.2)

11. HTTP Issues Cookies A way to deal with stateless nature of the HTTP
Key-value pairs (of strings) stored in the web browser
Set by special HTTP response header
Automatically re-sent in headers with every request
Each page (domain) has it own set of cookies
Cookies in PHP
Cookies sent by browser are loaded to $_COOKIE[]
Cookies are set/modified/removed by setcookie()
The function modifies HTTP response headers
Cookies are usually used along with a mechanism that allows keeping session specific data at the server side. PHP supports sessions directly (see documentation).
Example 4
by Martin Kruliš (v1.2)

12. Databases MySQL Original mysql API is deprecated (as of PHP 5.5)
MySQL Improved (mysqli) API
Dual object/procedural interface
Procedural interface is similar to original (deprecated) API
Advanced connectivity features
Persistent connections, compression, encryption
Directly supports transactions
MySQL Native Driver (mysqlnd) extension
More direct access to MySQL server
Additional features (e.g., asynchronous queries)
by Martin Kruliš (v1.2)

13. Databases MySQLi Procedural API
Establishing connection with MySQL server
$mysqli = mysqli_connect("server", "login", "password", "db_name");
Performing queries
$res = mysqli_query($mysqli, "SQL …");
Terminating connection
mysqli_close($mysqli);
Safe way to include strings in SQL query
mysqli_real_escape_string($mysqli, $str);
by Martin Kruliš (v1.2)

14. Databases MySQL Results
mysqli_query() result depends on the query type
On failure always returns false
Modification queries return true on success
Data queries (SELECT, …) return mysqli_result obj
mysqli_fetch_assoc($res)
mysqli_fetch_obj($res)
mysqli_fetch_all($res, $format)
mysqli_fetch_fields($res)
mysqli_num_rows($res)
mysqli_free_result($res)
by Martin Kruliš (v1.2)

15. Placeholders ? can be used for bound variables
Databases
Placeholders ? can be used for bound variables
MySQLi Prepared Statements
Prepare new MySQL statement
$stmt = mysqli_stmt_init($mysqli); mysqli_stmt_prepare($stmt, "SELECT ...");
Binding parameters (by positional placeholders)
mysqli_stmt_bind_param($stmt, $types, $var1, …)
Types string – one char ~ one parameter
Execute and get result object
mysqli_stmt_execute($stmt);
$res = mysqli_stmt_get_result($stmt);
Example 5
by Martin Kruliš (v1.2)

16. Frameworks PHP Frameworks Symfony – one of the most popular
Laravel – one of the most popular
Slim - microframework
Zend – one of the oldest
Nette – Czech developer and comunity
CodeIgniter
Yii 2
Phalcon
CakePHP …
by Martin Kruliš (v1.2)

17. Discussion
by Martin Kruliš (v1.2)