PHP Crash Course: The Complete, Modern, Hands-On Guide

Cover....1 Title Page....4 Copyright....5 Dedication....6 About the Author....8 About the Technical Reviewers....8 Brief Contents....10 Contents in Detail....12 Acknowledgments....24 Introduction....26 Who This Book Is For....27 Why PHP?....27 What You Will Learn....27 Online Resources....30 Part I: Language Fundamentals....32 1. PHP Program Basics....34 Two Methods to Run PHP....34 The Replit Online Coding Environment....35 A Local PHP Installation....39 Template Text vs. PHP Code....44 Comments....46 Variables....47 Creating Variables....48 Using Variables....49 Naming Variables....49 Constants....51 Operators and Operands....52 Arithmetic Operators....52 Combined Arithmetic Assignment Operators....53 Increment and Decrement Operators....54 Summary....55 Exercises....55 2. Data Types....58 PHP Data Types....59 Scalar Data Types....59 The Special NULL Type....61 Functions to Test for a Data Type....62 Type Juggling....63 Numeric Contexts....64 String Contexts....66 Comparative Contexts....66 Logical and Other Contexts....70 Type Casting....70 Summary....71 Exercises....71 3. Strings and String Functions....72 Whitespace....73 Single-Quoted Strings....74 Joining Strings: Concatenation....75 Double-Quoted Strings....77 Handling the Character After a Variable Name....78 Incorporating Unicode Characters....79 Heredocs....80 Escape Sequences....81 Indention....81 Nowdocs....83 Built-in String Functions....84 Converting to Upper- and Lowercase....84 Searching and Counting....85 Extracting and Replacing Substrings....87 Trimming Whitespace....90 Removing All Unnecessary Whitespace....91 Repeating and Padding....92 Summary....93 Exercises....93 4. Conditionals....96 Conditions Are True or False....97 if Statements....97 if...else Statements....98 Nested if...else Statements....99 if...elseif...else Statements....99 Alternative Syntax....100 Logical Operators....101 NOT....101 AND....102 OR....103 XOR....104 switch Statements....104 match Statements....106 The Ternary Operator....107 The Null-Coalescing Operator....108 Summary....109 Exercises....110 5. Custom Functions....112 Separating Code into Multiple Files....113 Reading in and Executing Another Script....113 Creating Absolute Filepaths....114 Declaring and Calling a Function....115 Parameters vs. Arguments....117 Errors from Incorrect Function Calls....118 Type Juggling....120 Functions Without Explicit Return Values....121 Returning NULL....122 Exiting a Function Early....123 Calling Functions from Within Functions....124 Functions with Multiple Return and Parameter Types....126 Nullable Types....126 Union Types....129 Optional Parameters....131 Positional vs. Named Arguments....133 Skipped Parameters....135 Pass-by-Value vs. Pass-by-Reference....136 Summary....138 Exercises....139 Part II: Working with Data....140 6. Loops....142 while Loops....143 do... while Loops....144 Boolean Flags....145 break Statements....147 for Loops....148 Using the Counter in the Loop....149 Skipping Loop Statements....150 Handling the Last Iteration Differently....151 Alternative Loop Syntax....153 Avoiding Infinite Loops....154 Summary....155 Exercises....155 7. Simple Arrays....156 Creating an Array and Accessing Its Values....157 Updating an Array....158 Appending an Element....158 Adding an Element with a Specific Key....159 Appending Multiple Elements....160 Removing the Last Element....161 Retrieving Information About an Array....162 Looping Through an Array....164 Using a foreach Loop....165 Accessing Keys and Values....165 Imploding an Array....166 Functions with a Variable Number of Arguments....167 Array Copies vs. Array References....168 Treating Strings as Arrays of Characters....170 Other Array Functions....172 Summary....172 Exercises....172 8. Sophisticated Arrays....174 Declaring Array Keys Explicitly....175 Arrays with Strings as Keys....177 Multidimensional Arrays....178 More Array Operations....180 Removing Any Element from an Array....180 Combining and Comparing Arrays....181 Destructuring an Array into Multiple Variables....183 Callback Functions and Arrays....184 Summary....186 Exercises....186 9. Files and Directories....188 Reading a File into a String....189 Confirming That a File Exists....190 Touching a File....192 Ensuring That a Directory Exists....192 Writing a String to a Text File....194 Managing Files and Directories....195 Reading a File into an Array....197 Using Lower-Level File Functions....197 Processing Multiple Files....199 JSON and Other File Types....202 Summary....204 Exercises....204 Part III: Programming Web Applications....206 10. ClientServer Communication and Web Development Basics....208 The HTTP Request-Response Cycle....209 Response Status Codes....210 An Example GET Request....211 How Servers Operate....213 Simple Web Servers for File Retrieval....213 Dynamic Web Servers for Processing Data....214 The Routing Process....215 Templating....216 PHP Tags....218 Short Echo Tags....219 The Model-View-Controller Architecture....219 Structuring a PHP Web Development Project....221 Summary....224 Exercises....224 11. Creating and Processing Web Forms....226 Basic ClientServer Communication for Web Forms....227 GET vs. POST Requests....228 A Simple Example....230 The filter_input() Function....235 Other Ways to Send Data....237 Sending Noneditable Data Along with Form Variables....237 Processing Mixed Query-String and POST Variables....238 Offering Multiple Submit Buttons....239 Encoding Data in Hyperlinks....242 Other Form Input Types....245 Radio Buttons....246 Checkboxes....247 Single-Selection Lists....251 Multiple-Selection Lists....252 Summary....254 Exercises....254 12. Validating Form Data....256 Writing Custom Validation Logic....257 Managing Multiple Validation Errors....258 Testing for a Valid Zero Value....259 Displaying and Validating Forms in a Single Postback Script....261 Simple Validation Logic....262 Array-Based Validation Logic....266 Summary....269 Exercises....269 13. Organizing a Web Application....270 Front Controllers and the MVC Architecture....271 Separating Display and Logic Files....273 Creating the Front Controller....274 Writing the Display Scripts....274 Moving Website Logic into Functions....276 Designing a Secure Folder Structure....276 Simplifying the Front-Controller Script....277 Writing the Functions....277 Generalizing the Front-Controller Structure....279 Distinguishing Between Requested Pages....280 Building a Multipage Application....280 Summary....288 Exercises....288 Part IV: Storing User Data with Browser Sessions....290 14. Working with Sessions....292 A Web Browser Session....293 The session_start() and session_id() Functions....295 The _SESSION Superglobal Array....296 Updating a Stored Value....297 Unsetting a Value....300 Destroying the Session and Emptying the Session Array....301 Summary....304 Exercises....304 15. Implementing a Shopping Cart....306 The Shopping Cart File Structure....307 Defining the Product List....308 Creating the Products Array....309 Adding CSS....310 Displaying the Star Ratings....311 Creating the Template Script....312 Updating the Index Script....313 Designing the Shopping Cart....314 Creating the Front Controller....315 Managing the Product and Cart Arrays....315 Streamlining the Index Script....317 Creating a Header Template....318 Creating the Cart Display Template....319 Interacting with the Session....323 Updating the Cart-Retrieval Function....323 Implementing Cart-Manipulation Functions....324 Creating the Empty Cart Template....326 Finalizing the Front Controller....327 Adding Display Functions....328 Writing the switch Statement....328 Summary....330 Exercises....331 16. Authentication and Authorization....332 A Simple Login Form....333 Creating a Site with a Login Form....334 Defining the File Structure....335 Creating the Shared Page Content....335 Designing the Page Templates....338 Developing the Login Form....340 Writing the Front Controller....342 Implementing the Logic Functions....343 Creating the Error Page Template....345 Storing Login Data with Sessions....347 Updating the Front Controller....347 Writing the Login Function....348 Updating the Header Template....349 Updating the Banking Page Template....350 Offering a Logout Feature....350 Adding the Logout Function....351 Updating the Front Controller....351 Displaying the Logout Link....351 Displaying the Logged-in Username....352 Retrieving the Username....353 Updating the Navigation Bar....353 Updating the CSS....353 Summary....354 Exercises....354 Part V: Object-Oriented PHP....356 17. Introduction to Object-Oriented Programming....358 Classes and Objects....359 Creating Relationships Between Objects....361 Encapsulation and Information Hiding....362 Superclasses, Inheritance, and Overriding....362 The Flow of Control for Object-Oriented Systems....364 An Example Class Declaration....365 Summary....366 Exercises....367 18. Declaring Classes and Creating Objects....368 Declaring a Class....368 Creating an Object....370 Private Properties with Public Accessor Methods....372 Getting and Setting Private Properties....375 Screening for Invalid Data....375 Overriding Default Class Behavior with Magic Methods....377 Initializing Values with a Constructor Method....377 Converting Objects to Strings....380 Object Variables as References....382 Handling Missing Objects....382 Custom Methods and Virtual Attributes....384 Summary....385 Exercises....386 19. Inheritance....388 Inheritance as Generalization....389 Creating Objects from Subclasses....390 Using Multiple Levels of Inheritance....392 Protected Visibility....393 Abstract Classes....398 Overriding Inherited Methods....399 Augmenting Inherited Behavior....402 Preventing Subclassing and Overriding....405 Declaring a Class final....405 Declaring a Method final....406 Summary....408 Exercises....408 20. Managing Classes and Namespaces with Composer....412 Namespaces....413 Declaring a Classs Namespace....413 Using a Namespaced Class....414 Referencing Namespaces in Class Declarations....415 Composer....417 Installing and Testing Composer....417 Creating the composer.json Configuration File....417 Creating an Autoloader....419 Adding Third-Party Libraries to a Project....421 Where to Find PHP Libraries....423 Summary....424 Exercises....424 21. Efficient Template Design with Twig....426 The Twig Templating Library....427 How Twig Works....428 A Simple Example....429 Manipulating Objects and Arrays in Twig Templates....434 Twig Control Structures....437 Creating a Multipage Website with Twig....439 The File Structure and Dependencies....439 The Application Class....440 The Twig Templates....442 Twig Features to Improve Efficiency....444 Improved Page Styling with CSS....450 Summary....455 Exercises....456 22. Structuring an Object-Oriented Web Application....458 Separating Display and Front-Controller Logic....459 Using Multiple Controller Classes....461 Sharing Controller Features Through Inheritance....466 Summary....469 Exercises....469 23. Error Handling with Exceptions....472 The Basics of Exceptions....473 Throwing an Exception....473 Catching an Exception....477 Ending with a finally Statement....478 Using Multiple Exception Classes....480 Other Built-in Exception Classes....480 Custom Exception Classes....482 Call-Stack Bubbling....485 Summary....487 Exercises....487 24. Logging Events, Messages, and Transactions....490 Built-in PHP Resources for Logging....491 Predefined Constants for Severity Levels....491 Logging Functions....493 The Monolog Logging Library....495 Organizing Logs with Channels....496 Managing Logs According to Severity....497 Logging Exceptions....500 Logging to the Cloud....503 Summary....505 Exercises....505 25. Static Methods, Properties, and Enumerations....506 Storing Class-Wide Information....506 Static Properties vs. Class Constants....511 Utility Classes with Static Members....513 Sharing Resources Across an Application....516 Saving Resources with the Singleton Pattern....519 Enumerations....522 Backed Enums....525 An Array of All Cases....525 Summary....526 Exercises....526 26. Abstract Methods, Interfaces, and Traits....528 From Inheritance to Interfaces....529 Inheriting a Fully Implemented Method from a Superclass....529 Inheriting an Abstract Method....531 Requiring Method Implementations with Interfaces....533 Real-World Applications of Interfaces....540 Caching Approach 1: Using an Array....541 Caching Approach 2: Using a JSON File....545 Caching Approach 3: Creating a Cacheable Interface....547 Traits....552 Declaring Traits....553 Inserting Traits....555 Resolving Trait Conflicts....556 What to Use When?....556 Summary....558 Exercises....558 Part VI: Database-Driven Application Development....560 27. Introduction to Databases....562 Relational Database Basics....563 Database Management Systems....564 Structured Query Language....565 Databases and Web Application Architecture....566 Object-Oriented Programming....566 The Model-View-Controller Pattern....569 Summary....570 Exercises....570 28. Database Programming with the PDO Library....572 The PDO Library....573 A Simple Database-Driven Web Application....574 Setting Up the Database Schema....574 Writing the PHP Classes....578 Switching from MySQL to SQLite....582 A Multipage Database-Driven Web Application....584 Managing the Product Information....586 Implementing the Controller Logic....589 Designing the Templates....592 Summary....597 Exercises....597 29. Programming Crud Operations....600 Deleting Data....601 Deleting Everything from a Table....601 Deleting Individual Items by ID....604 Creating New Database Entries....608 Adding Products Through a Web Form....609 Highlighting the Newly Created Product....613 Updating a Database Entry....616 Avoiding Double Form Submission with Redirects....621 Summary....624 Exercises....625 30. Orm Libraries and Database Security....626 Simplifying Database Code with an ORM Library....627 Adding an ORM Library to a Project....629 Moving Database Credentials to a .env File....629 Relegating Product Operations to the ORM Library....630 Adding a New Database Table....632 Security Best Practices....639 Storing Hashed Passwords....639 Verifying Hashed Passwords at Login....640 Securing Database Credentials....646 The Doctrine ORM Library....646 Removing the Previous ORM Library....646 Adding Doctrine....647 Verifying That Doctrine Is Working....648 Creating Database Tables....649 Adding Records to a Table....652 Integrating Doctrine into the Application Code....653 Creating Foreign-Key Relationships....655 Summary....660 Exercises....660 31. Working with Dates and Times....662 The ISO 8601 Standard....663 Creating Dates and Times....664 Formatting the Date-Time Information....665 Using DateTimeImmutable vs. DateTime....666 Manipulating Dates and Times....668 Using Date-Time Intervals....670 Looping at Regular Intervals....671 Time Zones....672 Daylight Saving Time....675 Epochs and Unix Time....677 Date-Time Information in a Web Application....678 The Application Class....679 The Supporting Classes....681 The Templates....684 MySQL Dates....686 Summary....692 Exercises....693 A. Installing PHP....694 macOS....694 Linux....695 Windows....696 AMP Installations....698 B. Database Setup....700 MySQL....700 macOS and Windows....700 Linux....701 SQLite....702 Confirming the MySQL and SQLite Extensions....702 C. Replit Configuration....704 Changing the PHP Version....705 Adding the Composer Tool....706 Using the SQLite Database System....706 Serving Pages from the public Directory....707 Index....710 Back Cover....730