PHP = PHunctional Programming

Editor's Notes

• #3: Didn’t we just become fully OO with 5.3? Functional Programming is the extensive use of functions to move the application from one state to the next
• #5: Objective: Understand PHP bettter
• #7: This gives rise to HO functions. Since objects can be passed around and returned
• #8: Everything can be represented in the context of lambda expressions In school, we’re taught about Turing machines and Von Neumann Model
• #10: Pure functions: count. Exceptions are thrown, printing to the console Is time() a pure function?
• #11: Pure functions: count. Is time() a pure function?
• #12: const cannot be used to conditionally define constants. To define a global constant, it has to be used in the outermost scope: if (...) { const FOO = 'BAR'; // invalid } // but if (...) { define('FOO', 'BAR'); // valid } const accepts a static scalar (number, string or other constant like true, false, null, __FILE__), whereas define() takes any expression. Since PHP 5.6 constant expressions are allowed in const as well: const BIT_5 = 1 << 5; // valid since PHP 5.6, invalid previously define('BIT_5', 1 << 5); // always valid const takes a plain constant name, whereas define() accepts any expression as name. This allows to do things like this: for ($i = 0; $i < 32; ++$i) { define('BIT_' . $i, 1 << $i); } consts are always case sensitive, whereas define() allows you to define case insensitive constants by passing true as the third argument const simply reads nicer. It's a language construct instead of a function and also is consistent with how you define constants in classes. const defines a constant in the current namespace, while define() has to be passed the full namespace name: namespace A\B\C; // To define the constant A\B\C\FOO: const FOO = 'BAR'; define('A\B\C\FOO', 'BAR'); Since PHP 5.6 const constants can also be arrays, while define() does not support arrays yet. However arrays will be supported for both cases in PHP 7. const FOO = [1, 2, 3]; // valid in PHP 5.6 define('FOO', [1, 2, 3]); // invalid in PHP 5.6, valid in PHP 7.0 As consts are language constructs and defined at compile time they are a bit faster than define()s.
• #15: Adding a new strategy involves creating a new class. Ex. safeDivide
• #16: FP makes patterns disappear
• #19: No consistent API Cumbersome and verbose to use No currying Not immutable! They separate the loop away from your business logic
• #22: This gives rise to HO functions. Since objects can be passed around and returned
• #23: How to do it we let the compiler worry abo Variable functions ¶ PHP supports the concept of variable functions. This means that if a variable name has parentheses appended to it, PHP will look for a function with the same name as whatever the variable evaluates to, and will attempt to execute it. Among other things, this can be used to implement callbacks, function tables, and so forth. Variable functions won't work with language constructs such as echo, print, unset(), isset(), empty(), include,require and the like. Utilize wrapper functions to make use of any of these constructs as variable functions.
• #24: How to do it we let the compiler worry abo Variable functions ¶ PHP supports the concept of variable functions. This means that if a variable name has parentheses appended to it, PHP will look for a function with the same name as whatever the variable evaluates to, and will attempt to execute it. Among other things, this can be used to implement callbacks, function tables, and so forth. Variable functions won't work with language constructs such as echo, print, unset(), isset(), empty(), include,require and the like. Utilize wrapper functions to make use of any of these constructs as variable functions.
• #25: How to do it we let the compiler worry abo Variable functions ¶ PHP supports the concept of variable functions. This means that if a variable name has parentheses appended to it, PHP will look for a function with the same name as whatever the variable evaluates to, and will attempt to execute it. Among other things, this can be used to implement callbacks, function tables, and so forth. Variable functions won't work with language constructs such as echo, print, unset(), isset(), empty(), include,require and the like. Utilize wrapper functions to make use of any of these constructs as variable functions.
• #26: This gives rise to HO functions. Since objects can be passed around and returned
• #29: This is also known as point-free style
• #30: We can do this thanks to HO functions
• #34: This gives rise to HO functions. Since objects can be passed around and returned
• #37: Most errors are due to error in the data
• #38: This is a functor
• #39: You are documenting the fact that you’re using this type Option is a monad!
• #40: You are documenting the fact that you’re using this type Option is a monad!
• #41: Didn’t we just become fully OO with 5.3?
• #46: Didn’t we just become fully OO with 5.3? Functional Programming is the extensive use of functions to move the application from one state to the next