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• It is very popular for hosting Open Source projects
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php-intro-workshop

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What is PHP?

PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development [2]

Unlike other scripting languages that run directly in your computer, PHP will almost always run on a server.

Writing our first program

"Hello, World!"

The "Hello, World!" program is the simplest program you can write in any programming language. All it does is output "Hello, World!" [3]

Writing our first program

"Hello, World!"

With our "php-intro-workshop" project there is a sample hello-world.php file

Variables

A variable is a storage location associated with a name.  Variables contain an unknown quantity or information called value [4]

<?php
// 01.simple_variable.php

$name = 'Juan';
$x = 30;
$y = 1.123;

// print the values below
print "";

Rules for PHP Variables [5]

• A variable starts with the $ sign, followed by the name of the variable.
• A variable name must start with a letter or the underscore character.
• A variable name cannot start with a number.
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )

Using PHP Variables [5]

<?php
// 02.hello_name.php

$name = 'Juan';
print "Hello, $name!";
/** 
 * This will output:
 * Hello, Juan!
 */

Data Types

A Data Type Is classification identifying one of various types of data [6]

Data Types

PHP Defines eight data types [7]

• Four scalar types:
  • boolean (true or false)
  • integer (negative & positive non factional numbers & zero)
  • float (floating-point number, aka double)
  • string  (a series of characters)
• Two compound types:
  • array (we'll get to arrays later)
  • object (we won't get to objects)
• And finally two special types:
  • resource (we won't get to resource)
  • NULL (variable with no value)

Data Types

<?php
// 03.data_types.php

print gettype(true)      . PHP_EOL;      // bolean
print gettype(12345)     . PHP_EOL;      // integer
print gettype(1.2345)    . PHP_EOL;      // double
print gettype("Hello")   . PHP_EOL;      // string
print gettype([1, 2, 3]) . PHP_EOL;      // array
print gettype(new stdClass()) . PHP_EOL; // object
print gettype(null)      . PHP_EOL;      // NULL

PHP_EOL is a constant that represents the "End Of Line" symbol.

Operators

An operator in a programming language is a symbol that tells the [computer] to perform specific mathematical, relational or logical operation and produce final result. [8]

An operator is something that takes one or more values (or expressions, in programming jargon) and yields another value. [9]

Arithmetic Operators

Assignment Operator

<?php
// 04.assignment_operator.php
$a = 1;
$b = 2;
$three = $a + $b;

print $three;

The assignment operator "=" is used to assign a value to a variable. It is not used to compare!

Comparison Operators

Comparison Operator

<?php
// 05.comparison_operators.php

var_dump(1 == 2);       // FALSE
var_dump(1 < 2);        // TRUE
var_dump(1 <= 2);       // TRUE
var_dump(2 > 2);        // FALSE
var_dump(2 >= 2);       // TRUE
var_dump(1 == true);    // TRUE - same as (bool)1 == TRUE
var_dump(1 === true);   // FALSE - same as (int)1 === FALSE
var_dump(0 == false);   // TRUE - same as (bool)0 == FALSE
var_dump(0 === false);  // FALSE - same as (int)0 === FALSE

The assignment operator "=" is used to assign a value to a variable. It is not used to compare!

Arrays

An array in PHP is an ordered map.

A map is a type that associates values to keys [10]

Example

Example Multidimensional

<?php
// 06.arrays.php

$array = array(
    "key" => "value",
    1     => 1234,
    "multi" => array(
        "another key" => "Another Value"
    )
);

It is possible to have an array of arrays

What are arrays good for?

Think of an array as a specialized way of organizing and storing data [11].  

PHP offers a wide range of functions to help you deal with arrays

What are arrays good for?

<?php
//07.arrays_menu.php

$menu = [
    'shake' => [
        'vanilla ice cream',
        'milk'
    ],
    'tiramisu' => [
        'instant-espresso powder',
        'sugar',
        '4 large egg',
        'heavy cream'
    ]
    'burger' => [
        'beef patty',
        'lettuce',
        'tomatoes',
        'buns'
    ],
];

ksort($menu);

print_r($menu);

Flow Control or Control Structures

So far we have created programs that have no logic, they follow a straight line. 

Control Structures are used to build logic into our programs.

Control Structures in PHP [12]

PHP supports several control structures but we will only look into the following:

• If statements
• Else statements
• Elseif statements
• For loops
• Foreach loops

If Statements

If is a condition to check if something is true

<?php
// 08.if_statements.php

$number = 1;
if ($number === 1) {
    print "The number variable is equals to one.";
}

$string = "Foo Bar";
if (strpos($string, "Foo") !== false) {
    print "The string '$string' contains the word 'Foo'";
}

Else Statements

If you want to take an action If a condition is not met, use the else statement

<?php
// 09.else_statements.php

$number = 4;
if ($number === 1) {
    print "The number variable is equal to one.";
} else {
    print "The number variable IS NOT equal to one.";
}

$string = "Lala Bar";
if (strpos($string, "Foo") !== false) {
    print "The string '$string' contains the word 'Foo'";
} else {
    print "The word 'Foo' WAS NOT found in the string '$string'";
}

Elseif Statements

It is a combination of else and if. It is used to link multiple conditions.

<?php
// 10.elseif_statements.php

$number = 4;

if ($number === 1) {
    print "The number variable is equal to one.";
} elseif ($number === 2) {
    print "The number variable is equal to two.";
} elseif ($number === 3) {
    print "The number variable is equal to three.";
} else {
    print "I give up I don't know what the number is :(";
}

Loops

A loop allows us to repeat a piece of code many times. 

Each time we loop we can make small changes to our program in order to get a desired output.

Loops [13]

Imagine you want to print all the numbers from 1 to 10

<?php
// 11.for_loops.php
// old way
print 1;
print 2;
// ...
print 10;

Loops can be used to iterate over arrays

<?php
// 12.for_loops_fib.php
$fib = [1, 2, 3, 5, 8, 13, 21, 34, 55, 89];
$size = sizeof($fib);

for($i = 0; $i < $size; $i++) {
    print $fib[$i];
}

// We can also create this same series 
// using simple math. 
$a = 1;
$b = 2;
print $a;
print $b;

for($i = 0; $i < $size-2; $i++) {
    $newB = $a+$b;
    $a = $b;
    $b = $newB;
    print $newB;
}

Foreach Loops

<?php
// 13.foreach_loops_fib.php
$fib = [1, 2, 3, 5, 8, 13, 21, 34, 55, 89];

foreach($fib as $number) {
    print $number;
}

Foreach loops are meant to iterate over arrays or collections of objects

First real application

Open the website directory. In there you will find several files. You only need to modify fibonacci.php and time.php

Open in the browser index.html

This file contains further information about this exercise

Display Time.

This website has a simple snipet of code written in JavaScript that will call two php files: time.php and fibonacci.php. You do not have to modify this file, just the PHP files.

Modify the time.php file to print the current time. Use the PHP Date Documentation to aid you with this task.

Fibonacci Series

Modify the fibonacci.php file to print a json encoded array with the current number and the previous number in the series up to 200 K, after that reset the series and start all over again. Use the PHP json_encode Documentation to print a json encoded array. You will find each number that you need in the super global $_GET['fib_1'] and $_GET['fib_2']