PHP 5 Strings

 

A string is a sequence of characters, like "Hello world!".

PHP String Functions

In this chapter we will look at some commonly used functions to manipulate strings.

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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!"); // outputs 12
?> 

 

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!"); // outputs 2
?> 

 

Reverse a String

The PHP strrev() function reverses a string:

Example

<?php
echo strrev("Hello world!"); // outputs !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"); // outputs 6
?> 

 

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!"); // outputs Hello Dolly!
?> 

 

 

 

 

 

 

 

PHP 5 Data Types

 

PHP 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;
?>

 

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);
?>

 

 

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);
?> 

 

 

PHP Boolean

A Boolean represents two possible states: TRUE or FALSE.

$x = true;
$y = false;

Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.

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PHP Array

An array stores multiple values in one single variable.
In the following example $cars is an array. The PHP var_dump() function returns the data type and value:

Example

<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?> 

 

 

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;
?> 

 

PHP NULL Value

Null is a special data type which can have only one value: NULL.
A variable of data type NULL is a variable that has no value assigned to it.
Tip: 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);
?> 

 

 

 

 

 

 

 

 

PHP 5 echo and print Statements

 

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

In this tutorial we use echo (and print) in almost every example. So, this chapter contains a little more info about those two output statements.

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PHP echo and print Statements

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.

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The PHP 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 "<h2>PHP is Fun!</h2>";
echo "Hello world!<br>";
echo "I'm about to learn PHP!<br>";
echo "This ", "string ", "was ", "made ", "with multiple parameters.";
?> 

 

 

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!";
?> 

 

 

 

 

PHP 5 Variables

 

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;
?>

 

PHP Variables

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).
Rules for PHP variables:

• 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 = "W3Schools.com";
echo "I love $txt!";
?>

 

PHP is a Loosely Typed Language

In the example above, notice that we did not have to tell PHP which data type the variable is.
PHP automatically converts the variable to the correct data type, depending on its value.
In other languages such as C, C++, and Java, the programmer must declare the name and type of the variable before using it.

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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 "<p>Variable x inside function is: $x</p>";
}
myTest();

echo "<p>Variable x outside function is: $x</p>";
?> 

 

 

 

 

 

PHP 5 Installation

What Do I Need?

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

Basic PHP Syntax

A PHP script can be placed anywhere in the document.
A PHP script starts with <?php and ends with ?>:

Example

 <!DOCTYPE html>
<html>
<body>

<h1>My first PHP page</h1>

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

</body>
</html> 

 

 

 

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

<!DOCTYPE html>
<html>
<body>

<?php
echo "My first PHP script!";
?>

</body>
</html>  

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

PHP is an amazing and popular language!

It is powerful enough to be at the core of the biggest blogging system on the web (WordPress)!
It is deep enough to run the largest social network (Facebook)!
It is also easy enough to be a beginner's first server side language!

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