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PHP Notes

1. Introduction to PHP & Features
1. PHP Scripts
1. Data Types
1. Variables
1. Operators
1. Control Structures
1. Working with Arrays
1. Functions
1. Working with Files
1. Working with Databases

1. Introduction to PHP & Features

PHP is a server scripting language, and a powerful tool for making dynamic and interactive Web pages.

PHP is a widely-used, free, and efficient alternative to competitors such as Microsoft's ASP.

Example

    <?php
        echo "Hellow World!";
    ?>

What You Should Already Know

Before you continue you should have a basic understanding of the following:

HTML
CSS
JavaScript

What is PHP?

PHP is an acronym for "PHP: Hypertext Preprocessor"
PHP is a widely-used, open source scripting language
PHP scripts are executed on the server
PHP is free to download and use

What is a PHP File?

PHP files can contain text, HTML, CSS, JavaScript, and PHP code
PHP code are executed on the server, and the result is returned to the browser as plain HTML
PHP files have extension ".php"

What Can PHP Do?

PHP can generate dynamic page content
PHP can create, open, read, write, delete, and close files on the server
PHP can collect form data
PHP can send and receive cookies
PHP can add, delete, modify data in your database
PHP can be used to control user-access
PHP can encrypt data
With PHP you are not limited to output HTML. You can output images, PDF files, and even Flash movies. You can also output any text, such as XHTML and XML.

Why PHP?

PHP runs on various platforms (Windows, Linux, Unix, Mac OS X, etc.)
PHP is compatible with almost all servers used today (Apache, IIS, etc.)
PHP supports a wide range of databases
PHP is free. Download it from the official PHP resource: www.php.net
PHP is easy to learn and runs efficiently on the server side

To start using PHP, you can:

Find a web host with PHP and MySQL support
Install a web server on your own PC, and then install PHP and MySQL

Use a Web Host with PHP Support

If your server has activated support for PHP you do not need to do anything.
Just create some .php files, place them in your web directory, and the server will automatically parse them for you.
You do not need to compile anything or install any extra tools.
Because PHP is free, most web hosts offer PHP support.
Set Up PHP on Your Own PC

However, if your server does not support PHP, you must:

install a web server install PHP install a database, such as MySQL

2. PHP Scripts

Basic PHP Syntax

A PHP script can be placed anywhere in the document.
A PHP script starts with <?php and ends with ?>
PHP statements end with a semicolon (;)

<?php
    //PHP code goes here
?>

Comments in PHP

A comment in PHP code is a line that is not read/executed as part of the program.
Its only purpose is to be read by someone who is looking at the code.

Comments can be used to:

Let others understand what you are doing
Remind yourself of what you did - Most programmers have experienced coming back to their own work a year or two later and having to re-figure out what they did.
Comments can remind you of what you were thinking when you wrote the code

Example

<?php
    // This is a single-line comment

    # This is also a single-line comment

    /*
        This is a multiple-lines comment
        block that spans over multiple
        lines
    */

    // You can also use comments to leave out parts of a code line
    $x = 5 /* + 15 */ + 5;
    echo $x;
?>

Output

3. Data Types

Variables can store data of different types, and different data types can do different things.
PHP supports the following data types:
- String
- Integer
- Float (floating point numbers - also called double)
- Boolean
- Array
- Object
- NULL
- Resource

PHP String

A string is a sequence of characters, like "Hello world!".
A string can be any text inside quotes. You can use single or double quotes:

Example

    <?php
        $x = "Hello world!";
        $y = 'Hello world!';
        echo $x;
        echo "<br>";
        echo $y;
    ?>

Output

Hello world!
Hello world!

String Functions

Get The Length of a String
The PHP strlen() function returns the length of a string.
The example below returns the length of the string "Hello world!":

Example

    <?php
        echo strlen("Hello world!");
    ?>

Output

Count The Number of Words in a String

The PHP str_word_count() function counts the number of words in a string.

Example

<?php
    echo str_word_count("Hello world!");
?>

Output

Reverse a String

The PHP strrev() function reverses a string.

Example

<?php
    echo strrev("Hello world!");
?>

Output

!dlrow olleH

Search For a Specific Text Within a String

The PHP strpos() function searches for a specific text within a string.
If a match is found, the function returns the character position of the first match.
If no match is found, it will return FALSE.
The example below searches for the text "world" in the string "Hello world!".

Example

<?php
    echo strpos("Hello world!", "world");
?>

Output

Replace Text Within a String

The PHP str_replace() function replaces some characters with some other characters in a string.
The example below replaces the text "world" with "Dolly".

Example

<?php
    echo str_replace("world", "Dolly", "Hello world!");
?>

Output

Hello Dolly!

PHP Integer

An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647.

Rules for integers

An integer must have at least one digit
An integer must not have a decimal point
An integer can be either positive or negative
Integers can be specified in three formats: decimal (10-based), hexadecimal (16- based - prefixed with 0x) or octal (8-based - prefixed with 0)
In the following example $x is an integer. The PHP var_dump() function returns the data type and value.

Example

<?php
    $x = 5985;
    var_dump($x);
?>

Output

int(5985)

PHP Float

A float (floating point number) is a number with a decimal point or a number in exponential form.
In the following example $x is a float. The PHP var_dump() function returns the data type and value.

Example

<?php
    $x = 10.365;
    var_dump($x);
?>

Output

float(10.365)

PHP Boolean

A Boolean represents two possible states: TRUE or FALSE.

$x = true;
$y = false;

Booleans are often used in conditional testing.

PHP Array

An array stores multiple values in one single variable.
An array is a special variable, which can hold more than one value at a time.
If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this.

$cars1 = "Volvo";
$cars2 = "BMW";
$cars3 = "Toyota";

However, what if you want to loop through the cars and find a specific one?
And what if you had not 3 cars, but 300?
The solution is to create an array!
An array can hold many values under a single name, and you can access the values by referring to an index number.
In PHP, the array() function is used to create an array: array();

Example

<?php
    $cars = array("Volvo", "BMW", "Toyota");
    echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>

Output

I like Volvo, BMW and Toyota.

In PHP, there are three types of arrays:
- Indexed arrays - Arrays with a numeric index
- Associative arrays - Arrays with named keys
- Multidimensional arrays - Arrays containing one or more arrays

4. Variables

Variables are "containers" for storing information.
Creating (Declaring) PHP Variables : In PHP, a variable starts with the $ sign, followed by the name of the variable.

Example

<?php
    $txt = "Hello world!";
    $x = 5;
    $y = 10.5;
    echo $txt;
    echo "<br>";
    echo $x;
    echo "<br>";
    echo $y;
?>

After the execution of the statements above
- the variable $txt will hold the value Hello world!
- the variable $x will hold the value 5
- the variable $y will hold the value 10.5

Output

Hello world!
5
10.5

Note

When you assign a text value to a variable, put quotes around the value.
Unlike other programming languages, PHP has no command for declaring a variable.
It is created the moment you first assign a value to it.

Rules for PHP variables:

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).
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 _ )
Variable names are case-sensitive ($age and $AGE are two different variables)

Output Variables

The PHP echo statement is often used to output data to the screen.
The following example will show how to output text and a variable.

Example

<?php
    $txt = "Hogwarts";
    echo "I love $txt!";
?>

Output

I love Hogwarts!

Example

<?php
    $txt = "Hogwarts";
    echo "I love " . $txt . "!";
?>

Output

I love Hogwarts!

Example

<?php
    $x = 5;
    $y = 4;
    echo $x + $y;
?>

Output

PHP Variables Scope

In PHP, variables can be declared anywhere in the script.
The scope of a variable is the part of the script where the variable can be referenced/used.
PHP has three different variable scopes:
- local
- global
- static

Global and Local Scope

A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function.

Example

<?php
    $x = 5; // global scope
    function myTest() {
        // using x inside this function will generate an error
        echo "Variable x inside function is: $x";
    }
    myTest();
    echo "Variable x outside function is: $x";
?>

Output

Variable x inside function is:
Variable x outside function is: 5

A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function.

Example

<?php
    function myTest() {
        $x = 5; // local scope
        echo "Variable x inside function is: $x";
    }
    myTest();
    // using x outside the function will generate an error
    echo "Variable x outside function is: $x";
?>

Output

Variable x inside function is: 5
Variable x outside function is:

The global Keyword

The global keyword is used to access a global variable from within a function.
To do this, use the global keyword before the variables (inside the function).

Example

<?php
    $x = 5;
    $y = 10;

    function myTest() {
        global $x, $y;
        $y = $x + $y;
    }

    myTest(); // run function
    echo $y; // output the new value for variable $y
?>

Output

The static Keyword

Normally, when a function is completed/executed, all of its variables are deleted.
However, sometimes we want a local variable NOT to be deleted. We need it for a further job.
To do this, use the static keyword when you first declare the variable.

Example

<?php
    function myTest() {
        static $x = 0;
        echo $x;
        $x++;
    }
    myTest();
    echo "<br>";
    myTest();
    echo "<br>";
    myTest();
?>

Output

0
1
2

`echo` and `print` Statements

- In PHP there are two basic ways to get output: `echo` and `print`

In most of the examples here we have used echo (and print).
echo and print are more or less the same.
They are both used to output data to the screen.
The differences are small:
- echo has no return value while print has a return value of 1 so it can be used in expressions.
- echo can take multiple parameters (although such usage is rare) while print can take one argument.
- echo is marginally faster than print.

`echo` Statement

The echo statement can be used with or without parentheses: echo or echo().

Display Text

The following example shows how to output text with the echo command (notice that the text can contain HTML markup).

Example

<?php
    echo "PHP is Fun!<br>";
    echo "Hello world!<br>";
    echo "I'm about to learn PHP!<br>";
    echo "This ", "string ", "was ", "made ", "with multiple parameters.";
?>

Output

PHP is Fun!
Hello world!
I'm about to learn PHP!
This string was made with multiple parameters.

Display Variables

The following example shows how to output text and variables with the echo statement.

Example

<?php
    $txt1 = "Learn PHP";
    $txt2 = "Hogwarts";
    $x = 5;
    $y = 4;
    echo "<h2>" . $txt1 . "</h2>";
    echo "Study PHP at " . $txt2 . "<br>";
    echo $x + $y;
?>

Output

Learn PHP
Study PHP at Hogwarts
9

The PHP `print` Statement

The print statement can be used with or without parentheses: print or print().

Display Text

The following example shows how to output text with the print command (notice that the text can contain HTML markup).

Example

<?php
    print "<h2>PHP is Fun!</h2>";
    print "Hello world!<br>";
    print "I'm about to learn PHP!";
?>

Output

PHP is Fun!
Hello world!
I'm about to learn PHP!

Display Variables

The following example shows how to output text and variables with the print statement.

Example

<?php
    $txt1 = "Learn PHP";
    $txt2= "Hogwarts";
    $x = 5;
    $y = 4;
    print "<h2>" . $txt1 . "</h2>";
    print "Study PHP at " . $txt2 . "<br>";
    print $x + $y;
?>

Output

Learn PHP
Study PHP at Hogwarts
9

PHP Object

An object is a data type which stores data and information on how to process that data.
In PHP, an object must be explicitly declared.
First we must declare a class of object.
For this, we use the class keyword.
A class is a structure that can contain properties and methods.

Example

<?php
    class Car {
        function Car() {
            $this->model = "VW";
        }
    }

    // create an object
    $herbie = new Car();
    // show object properties
    echo $herbie->model;
?>

Output

VW

PHP Objects

An Object is an individual instance of the data structure defined by a class.
We define a class once and then make many objects that belong to it.
Objects are also known as instances.

Creating an Object:

Following is an example of how to create object using new operator.

<?php
    class Books {
        var $price;
        var $title;

        function setPrice($par){
            $this->price = $par;
        }

        function getPrice(){
            echo $this->price."<br>";
        }

        function setTitle($par){
            $this->title = $par;
        }

        function getTitle(){
            echo $this->title."<br>" ;
        }
    }
    $maths = new Books;
    $maths->setTitle( "Algebra" );  /* Setting title and prices for the object */
    $maths->setPrice( 7 );
    $maths->getTitle();
    $maths->getPrice();             /* Calling Member Functions */  
?>

PHP NULL Value

Null is a special data type which ca n have only one value: NULL.
A variable of data type NULL is a variable that has no value assigned to it.
If a variable is created without a value, it is automatically assigned a value of NULL.
Variables can also be emptied by setting the value to NULL.

Example

<?php
    $x = "Hello world!";
    $x = null;
    var_dump($x);
?>

Output

NULL

Constants

Constants are like variables except that once they are defined they cannot be changed or undefined.

PHP Constants

A constant is an identifier (name) for a simple value.
The value cannot be changed during the script.
A valid constant name starts with a letter or underscore (no $ sign before the constant name).
Note: Unlike variables, constants are automatically global across the entire script.

Create a PHP Constant

To create a constant, use the define() function.

Syntax

    define(name, value, case-insensitive)

Parameters:

name: Specifies the name of the constant
value: Specifies the value of the constant
case-insensitive: Specifies whether the constant name should be case- insensitive. Default is false.
The example below creates a constant with a case-sensitive name.

Example

<?php
    // case-sensitive constant name
    define("GREETING", "Welcome to Hogwarts!");
    echo GREETING;
?>

Output

Welcome to Hogwarts!

The example below creates a constant with a case-insensitive name:

Example

<?php
    // case-insensitive constant name
    define("GREETING", "Welcome to Hogwarts!", true);
    echo greeting;
?>

Output

Welcome to Hogwarts!

Constants are Global

Constants are automatically global and can be used across the entire script.
The example below uses a constant inside a function, even if it is defined outside the function.

Example

<?php
    define("GREETING", "Welcome to Hogwarts!");
    function myTest() {
        echo GREETING;
    }
    myTest();
?>

Output

Welcome to Hogwarts!

5. Operators

Operators are used to perform operations on variables and values.

PHP divides the operators in the following groups

Arithmetic operators
Assignment operators
Comparison operators
Increment/Decrement operators
Logical operators
String operators
Array operators

PHP Arithmetic Operators

The PHP arithmetic operators are used with numeric values to perform common arithmetical operations, such as addition, subtraction, multiplication etc.

Operator	Name	Example	Result
`+`	Addition	`$x + $y`	Sum of `$x` and `$y`
`-`	Subtraction	`$x - $y`	Difference of `$x` and `$y`
`*`	Multiplication	`$x * $y`	Product of `$x` and `$y`
`/`	Division	`$x / $y`	Quotient of `$x` and `$y`
`%`	Modulus	`$x % $y`	Remainder of `$x` divided by `$y`
`**`	Exponentiation	`$x ** $y`	Result of raising `$x` to the `$y`'th power (Introduced in PHP 5.6)

PHP Assignment Operators

The PHP assignment operators are used with numeric values to write a value to a variable.
The basic assignment operator in PHP is "=".
It means that the left operand gets set to the value of the assignment expression on the right.

Assignment	Same as	Description
`x += y`	`x = x + y`	Addition
`x -= y`	`x = x - y`	Subtraction
`x *= y`	`x = x * y`	Multiplication
`x /= y`	`x = x / y`	Division
`x %= y`	`x = x % y`	Modulus

PHP Comparison Operators

The PHP comparison operators are used to compare two values (number or string).

Operator	Name	Example	Result
`==`	Equal	`$x == $y`	Returns `true` if `$x` is equal to `$y`
`===`	Identical	`$x === $y`	Returns `true` if `$x` is equal to `$y`, and they are of the same type
`!=`	Not equal	`$x != $y`	Returns `true` if `$x` is not equal to `$y`
`<>`	Not equal	`$x <> $y`	Returns `true` if `$x` is not equal to `$y`
`!==`	Not identical	`$x !== $y`	Returns `true` if `$x` is not equal to `$y`, or they are not of the same type
`>`	Greater than	`$x > $y`	Returns `true` if `$x` is greater than `$y`
`<`	Less than	`$x < $y`	Returns `true` if `$x` is less than `$y`
`>=`	Greater than or equal to	`$x >= $y`	Returns `true` if `$x` is greater than or equal to `$y`
`<=`	Lesser than or equal to	`$x <= $y`	Returns `true` if `$x` is less than or equal to `$y`

PHP Increment / Decrement Operators

The PHP increment operators are used to increment a variable's value by one.
The PHP decrement operators are used to decrement a variable's value by one.

Operator	Name	Description
`++$x`	Pre-increment	Increments `$x` by one, then returns `$x`
`$x++`	Post-increment	Returns `$x`, then increments `$x` by one
`--$x`	Pre-decrement	Decrements `$x` by one, then returns `$x`
`$x--`	Post-decrement	Returns `$x`, then decrements `$x` by one

PHP Logical Operators

The PHP logical operators are used to combine conditional statements.

| Operator | Name | Example     | Result                                        |
| -------- | ---- | ----------- | --------------------------------------------- |
| and      | And  | $x and $y   | true if both $x and $y are true               |
| or       | Or   | $x or $y    | true if either $x or $y is true               |
| xor      | XOR  | $x xor $y   | true if either $x or $y is true, but not both |
| &&       | And  | $x && $y    | true if both $x and $y are true               |
| ||       | Or   | $x || $y    | true if either $x or $y is true               |
| !        | Not  | !$x         | true if $x is not true                        |

PHP String Operators

PHP has two operators that are specially designed for strings.

Operator	Name	Example	Result
`.`	Concatenation	`$txt1 . $txt2`	Concatenation of `$txt1` and `$txt2`
`.=`	Concatenation assignment	`$txt1 .= $txt2`	Appends `$txt2` to `$txt1`

PHP Array Operators

Operator	Name	Example	Result
`+`	Union	`$x + $y`	Union of `$x` and `$y`
`==`	Equality	`$x == $y`	Returns `true` if `$x` and `$y` have the same key/value pairs
`===`	Identity	`$x === $y`	Returns `true` if `$x` and `$y` have the same key/value pairs in the same order and of the same types
`!=`	Inequality	`$x != $y`	Returns `true` if `$x` is not equal to `$y`
`<>`	Inequality	`$x <> $y`	Returns `true` if `$x` is not equal to `$y`
`!==`	Non-identity	`$x !== $y`	Returns `true` if `$x` is not identical to `$y`

PHP Conditional Statements

Very often when you write code, you want to perform different actions for different conditions.
You can use conditional statements in your code to do this.

In PHP we have the following conditional statements:

if statement - executes some code if one condition is true
if...else statement - executes some code if a condition is true and another code if that condition is false
if...elseif....else statement - executes different codes for more than two conditions
switch statement - selects one of many blocks of code to be executed

The if Statement

The if statement executes some code if one condition is true.

Syntax

if (condition) {
    // code to be executed if condition is true;
}

The example below will output "Have a good day!" if the current time (HOUR) is less than 20.

Example

<?php
    $t = date("H");
    if ($t < "20") {
        echo "Have a good day!";
    }
?>

Output

Have a good day!

The if...else Statement

The if....else statement executes some code if a condition is true and another code if that condition is false.

Syntax

if (condition) {
    // code to be executed if condition is true;
} else {
    // code to be executed if condition is false;
}

The example below will output "Have a good day!" if the current time is less than 20, and "Have a good night!" otherwise.

Example

<?php
    $t = date("H");
    if ($t < "20") {
        echo "Have a good day!";
    } else {
        echo "Have a good night!";
    }
?>

Output

Have a good day!

The if... elseif ....else Statement

The if.... elseif... else statement executes different codes for more than two conditions.

Syntax

if (condition) {
    // code to be executed if this condition is true;
} else if (condition) {
    // code to be executed if this condition is true;
} else {
    // code to be executed if all conditions are false;
}

The example below will output "Have a good morning!" if the current time is less than 10, and "Have a good day!" if the current time is less than 20.
Otherwise it will output "Have a good night!".

Example

<?php
    $t = date("H");
    echo "<p>The hour (of the server) is " . $t;
    echo ", and will give the following message:</p>";
    if ($t < "10") {
        echo "Have a good morning!";
    }   elseif ($t < "20") {
        echo "Have a good day!";
    }  else {
        echo "Have a good night!";
    }
?>

Output

The hour (of the server) is 01, and will give the following message:
Have a good morning!

The switch Statement

The switch statement is used to perform different actions based on different conditions.
Use the switch statement to select one of many blocks of code to be executed.

Syntax

switch (n) {
    case label1:
        // code to be executed if n=label1;
        break;
    case label2:
        // code to be executed if n=label2;
        break;
    case label3:
        // code to be executed if n=label3;
        break;
    ...
    default:
        // code to be executed if n is different from all labels;
}

This is how it works:

First we have a single expression n (most often a variable), that is evaluated once.
The value of the expression is then compared with the values for each case in the structure.
If there is a match, the block of code associated with that case is executed.
Use break to prevent the code from running into the next case automatically.
The default statement is used if no match is found.Example

<?php
    $favcolor = "red";
    switch ($favcolor) {
        case "red":
            echo "Your favorite color is red!";
            break;
        case "blue":
            echo "Your favorite color is blue!";
            break;
        case "green":
            echo "Your favorite color is green!";
            break;
        default:
            echo "Your favorite color is neither red, blue, nor green!";
    }
?>

Output

Your favorite color is red!

PHP Loops

Often when you write code, you want the same block of code to run over and over again in a row.
Instead of adding several almost equal code-lines in a script, we can use loops to perform a task like this.
In PHP, we have the following looping statements:
- while - loops through a block of code as long as the specified condition is true
- do...while - loops through a block of code once, and then repeats the loop as long as the specified condition is true
- for - loops through a block of code a specified number of times
- foreach - loops through a block of code for each element in an array

The PHP while Loop

The while loop executes a block of code as long as the specified condition is true.

Syntax

while (condition is true) {
    // code to be executed;
}

The example below first sets a variable $x to 1 ($x = 1).
Then, the while loop will continue to run as long as $x is less than, or equal to 5 ($x <= 5).
$x will increase by 1 each time the loop runs ($x++).

Example

<?php
    $x = 1;
    while($x <= 5) {
        echo "The number is: $x<br>";
        $x++;
    }
?>

Output

The number is: 1
The number is: 2
The number is: 3
The number is: 4
The number is: 5

The PHP do...while Loop

The do...while loop will always execute the block of code once, it will then check the condition, and repeat the loop while the specified condition is true.

Syntax

do {
    // code to be executed;
} while (condition is true);

The example below first sets a variable $x to 1 ($x = 1).
Then, the do while loop will write some output, and then increment the variable $x with 1.
Then the condition is checked (is $x less than, or equal to 5?), and the loop will continue to run as long as $x is less than, or equal to 5:

Example

<?php
    $x = 1;
    do {
        echo "The number is: $x <br>";
        $x++;
    } while ($x <= 5);
?>

Output

The number is: 1
The number is: 2
The number is: 3
The number is: 4
The number is: 5

Notice that in a do while loop the condition is tested AFTER executing the statements within the loop.
This means that the do while loop would execute its statements at least once, even if the condition is false the first time.
The example below sets the $x variable to 6, then it runs the loop, and then the condition is checked.

Example

<?php
    $x = 6;
    do {
        echo "The number is: $x <br>";
        $x++;
    } while ($x <= 5);
?>

Output

The number is: 6

for Loops

PHP for loops execute a block of code a specified number of times.

The PHP for Loop

The for loop is used when you know in advance how many times the script should run.

Syntax

    for (init counter; test counter; increment counter) {
        // code to be executed;
    }

Parameters

init counter: Initialize the loop counter value
test counter: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
increment counter: Increases the loop counter value
The example below displays the numbers from 0 to 10:

Example

<?php
    for ($x = 0; $x <= 10; $x++) {
        echo "The number is: $x <br>";
    }
?>

Output

The number is: 0
The number is: 1
The number is: 2
The number is: 3
The number is: 4
The number is: 5
The number is: 6
The number is: 7
The number is: 8
The number is: 9
The number is: 10

The PHP foreach Loop

The foreach loop works only on arrays, and is used to loop through each key/value pair in an array.

Syntax

foreach ($array as $value)
{
    // code to be executed;
}

For every loop iteration, the value of the current array element is assigned to $value and the array pointer is moved by one, until it reaches the last array element.
The following example demonstrates a loop that will output the values of the given array ($colors):

Example

<?php
    $colors = array("red", "green", "blue", "yellow");
    foreach ($colors as $value) {
        echo "$value <br>";
    }
?>

Output

red
green
blue
yellow

Files

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README.md

PHP Notes

1. Introduction to PHP & Features

Example

What You Should Already Know

What is PHP?

What is a PHP File?

What Can PHP Do?

Why PHP?

To start using PHP, you can:

Use a Web Host with PHP Support

However, if your server does not support PHP, you must:

2. PHP Scripts

Basic PHP Syntax

Comments in PHP

Comments can be used to:

Example

Output

3. Data Types

PHP String

Example

Output

String Functions

Example

Output

Count The Number of Words in a String

Example

Output

Reverse a String

Example

Output

Search For a Specific Text Within a String

Example

Output

Replace Text Within a String

Example

Output

PHP Integer

Rules for integers

Example

Output

PHP Float

Example

Output

PHP Boolean

PHP Array

Example

Output

4. Variables

Example

Output

Note

Rules for PHP variables:

Output Variables

Example

Output

Example

Output

Example

Output

PHP Variables Scope

Global and Local Scope

Example

Output

Example

Output

The global Keyword

Example

Output

`echo` and `print` Statements

- In PHP there are two basic ways to get output: `echo` and `print`

`echo` Statement

The PHP `print` Statement