PHP for the Web: Visual QuickStart Guide Book

This book introduces PHP through well-explained, realistic examples. After exploring the basic concepts and syntax of PHP, it shows how to work with files and databases. It's not as straightforward as Head First PHP MySQL (my review), but it definitely covers a lot more ground. Each chapter ends with several tips (usually best practices) and suggestions for digging deeper.

Variables
• Use print for scalar (single-valued) variables, and print_r() for complex variables (arrays and objects).
• Items in single quotes are treated literally; items in double quotes are extrapolated (processed).

HTML Forms and PHP
• In forms, pass preset values using input type="hidden".
• Use GET to request info from the server; use POST to trigger a server-side action. GET sends info via URL; POST sends it invisibly.

Using Numbers
• number_format() rounds and formats.

Using Strings
• nl2br() converts newlines to break tags.
• htmlentities(), htmlspecialchars(), and strip_tags() make user-provided data safe to print to the browser.
• urlencode() encodes a string so it can be passed in a URL.
• trim() removes whitespace from the beginning and end of a string.

Control Structures
• empty() returns TRUE if a variable has no value, value of 0, or value of FALSE. isset() returns TRUE if a variable has any value, including 0, FALSE, or the empty string.
• break exits the current structure.
• continue terminates the current iteration of the loop and checks the loop condition again.
• exit and die terminate execution.
• for loop performs specific statements for a determined number of iterations.
• while loop continues as long as the condition is TRUE; most often used to retrieve from a database.
• do...while loop is same as while loop, but guarantees that statements are executed at least once.

Using Arrays
• foreach loop is used to iterate through an array.
• Wrap array constructs in curly brackets to avoid problems with quotation marks.
• There are several sorting functions to get by values or keys. Pay attention to maintaining key-value association if necessary.
• implode() turns an array into a string. join() is synonymous.
• explode() turns a string into an array.

Creating Web Applications
• Include files with include(), which warns but continues in case of errors, or require(), which terminates execution in case of errors. Generally avoid include_once() and require_once(), which adversely affect performance.
• Constants have unchanging values. Names are uppercase, with no initial $. Assign values with define().
• To test whether a form has been submitted, use if ($_SERVER['REQUEST_METHOD'] == 'POST') {.
• header() controls HTTP headers, and can be used to redirect to another page.

Cookies and Sessions
• setcookie() sends a cookie.
• Delete a cookie by sending a cookie with the cookie's name and a value of FALSE.
• Use cookies when security isn't a concern, and for < 4 KB of data. Use sessions for more security and more data.
• sesion_start() starts a session.
• Delete a session with $_SESSION = array(), then session_destroy(). To delete an individual session value, use unset().

Creating Functions
• In functions, arguments with default values must come after arguments without default values.
• global makes a variable global, usable outside the function.
• Put an @ in front of a function to suppress errors, notices, and warnings.
• file_put_contents() opens and writes a file.
• file() returns file contents as an array.

Files and Directories
• Put writable files and directories outside of the Web root directory, for security.
• move_uploaded_file() moves an uploaded file from the temp directory.
• md5() creates a hash.
• fgets() and fgetscsv() read files incrementally.

Intro to Databases
• mysqli_query() sends a SQL command to MySQL.
• mysqli_connect() opens a connection to MySQL; mysqli_close() closes it.
• mysqli_select_db selects the database.
• Don't use die() when a database error occurs; it's too heavy-handed.
• mysqli_real_escape_string() escapes potentially harmful characters.
• mysqli_fetch_array() fetches 1 row at a time.
• Use TRUNCATE rather than DELETE FROM to empty a table.
• mysqli_affected_rows() returns the number of records altered.
• Add LIMIT 1 to UPDATE queries to affect only 1 row.

PHP Learning Resources
• PHP.net
• Zend
• PHPBuilder
• PHP Zone
• php|architect
• W3Schools