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PHP $_GET Function

tutor — Mon, 14 Dec 2009 07:34:53 +0000

$_GET is a built-in function in PHP which is used to collect values in a form where the method is “get”.

Get method is rarely used though, as the information sent from a form with the GET method is visible to everyone in the browser’s address bar.

Also it has a limit on the amount of information that can be sent. All the information is concatenated in a single line and this line is printed on the browser’s address bar.

For eg:

When the user clicks the “Submit” button, the URL sent to the server could look something like this:

http://www.goweb99.com/data.php?username=Tutor&address=Capital+Federal

The “data.php” file can now use the $_GET function to collect form data (the names of the form fields will automatically be the keys in the $_GET array):

For eg:

Welcome ! to the world of PHP

You live at .

Get method should not be used when sending passwords or other sensitive information.

However, because the variables are displayed in the URL, it is possible to bookmark the page, which may serve some purpose.

PHP If Condition

tutor — Sat, 12 Dec 2009 10:47:58 +0000

The If Statement

This statement executes a piece of code only when a condition is true.

Syntax

if (condition) code to be executed if condition is true;

For eg:

$d=date(”D”);
if ($d==”Fri”) echo “Today is Friday!”;
?>

The if…else Statement

This is a two way condition evaluation, in which there are yes and no both lead to different code block.

We just add one else condition in the above if statement.

Syntax

For eg:

$d=date(”D”); if ($d==”Fri”)
echo “Today is Friday!”; else
echo “Today is not Friday!”;
?>

If more than one line should be executed, then the lines should be enclosed within curly braces:

$d=date(”D”);
if ($d==”Fri”)
{
echo “Hello!
”;
echo “Today is Friday!”;
}
?>

The if…elseif….else Statement

This construct is used when there are more conditions than just true or false.

When PHP evaluates If…elseif…else statement it first sees if the If statement is true. If that test comes out to be false it then checks the first elseif statement.

If then also the result comes out to be false it will check the next elseif statement, if there exists any more otherwise, it will evaluate the else segment, if one exists.

Syntax

For eg:

$d=date(”D”);   if ($d==”Fri”)
echo “Today is Friday!”;   elseif ($d==”Sun”)
echo “Today is Sunday!”;   else
echo “Today is neither Friday nor Sunday!”;
?>

Conditional Statements

tutor — Sat, 12 Dec 2009 10:08:36 +0000

Conditional statements are used to evaluate some conditions and perform different actions based on the outcome.

You can use conditional statements in your code to do this.

PHP provides the following conditional statements:

If statement – execute the piece of code only if a specified condition is true.
if (condition) code to be executed if condition is true;

If…else statement – this statement executes a two way condition, where the true part does something else and the false part executes something else.
if (condition)
code to be executed if condition is true;
else
code to be executed if condition is false;

If…elseif….else statement – if there are multi-way condition, where there are several blocks of code to be executed based on different conditions.
if (condition)
code to be executed if condition is true;
elseif (condition)
code to be executed if condition is true;
else
code to be executed if condition is false;

Switch statement – this statement is used to select one of many blocks of code to be executed
switch (n)
{
case label1:
code to be executed if n=label1;
break;
case label2:
code to be executed if n=label2;
break;
default:
code to be executed if n is different from both label1 and label2;
}

Combining Arithmetic & Assignment Operators

tutor — Sat, 12 Dec 2009 09:45:21 +0000

We often need to increment a variable by a fixed amount. For eg a variable which is being used to count something, may be a counter for a loop or some other purpose, we need to constantly increment it by 1.

$count = $count + 1;

However, there is another way for doing this.

$counter += 1;

This combined assignment/arithmetic operator would accomplish the same task as the above code.

Although this combined operator shortens the code but sometimes for those who are not accustomed to such programming constructs, this may create confusion and may make the code unreadable.0

Operator	Description	Example	Expanded Form
+=	Plus Equals	$x += 2;	$x = $x + 2;
-=	Minus Equals	$x -= 4;	$x = $x – 4;
*=	Multiply Equals	$x *= 3;	$x = $x * 3;
/=	Divide Equals	$x /= 2;	$x = $x / 2;
%=	Modulo Equals	$x %= 5;	$x = $x % 5;
.=	Concatenate Equals	$my_str.=”PHP”;	$my_str = $my_str .”PHP”;

PHP Operators

tutor — Sat, 12 Dec 2009 08:04:15 +0000

Operators are used to manipulate the values or directly or to operate on variables to manipulate values.

All the operators are categorized under the following:

Assignment Operators
Arithmetic Operators
Comparison Operators
String Operators

This section lists the different operators available in PHP.

Assignment Operators

Assignment operators assign a value to a variable, or the value of a variable to another variable.

$my_var = 4;
$another_var = $my_var;

Now both $my_var and $another_var contain the value 4.

Assignments can also be used in conjunction with arithmetic operators, which we will be studying later in this tutorial.

Arithmetic Operators

Operator	Description	Example
+	Addition	2 + 4
-	Subtraction	6-2
*	Multiplication	5*3
/	Division	15/3
%	Modulus	43%10

$addition= 2+3;
$subtraction= 3-2;
$multiplication= 2*3;
$division= 22/11;
$modulus = 5 % 2;

Comparison Operators

Comparison Operators are used to compare the values of two operators. These operators are used inside conditional statements and evaluate to either true or false. PHP provides all the comparison operators that are provided by other programming language.
Assume: $x = 4 and $y = 5;

Operator	Description	Example	Result
==	Equal To	$x == $y	false
!=	Not Equal To	$x != $y	true
<	Less Than	$x < $y	true
>	Greater Than	$x > $y	false
<=	Less Than or Equal To	$x <= $y	true
>=	Greater Than or Equal To	$x >= $y	false

String Operators

As we have learned before the dot operator is used to concatenate or join two strings.

$a_string=”Hello”;
$b_string=” Tutor”;
$new_string=$a_string . $_string;
Echo $new_string;

Output

Hello Tutor

Arrays

tutor — Fri, 11 Dec 2009 12:28:42 +0000

An array is a collection of similar type of values. It is a data structure which stores one or more similar type values as a single value. In PHP arrays are actually maps, ie each key is mapped to a value.

We are assuming that you have a basic knowledge of programming, so you must be knowing what are arrays.

If you are new to programming, then it may confuse you, as till now one variable can store only one value but this variable can store multiple values.

You may think an array as a container with many spaces where you can fill data according to your choice. Arrays group similar kind of data as it doesn’t make sense to store a set of like values in different variables.

For eg if you want to store your marks of different subject, if you have only 5 subjects then you can store them separately, but if you are having twenty or thirty subjects or even more then it will look very clumsy to use so much variables moreover it will be very tough to manage such number of variables.

You can define array using square brackets as:

$my_array[];

You can assign values to the array elements as:

$marks[0]=20;
$ marks [1]=10;

Araay can be understood using the key / value structure. Keys are the numbers specified in the array and the values are the marks. Each key of an array is associated with a value that we can manipulate and reference.

The general form to set the key of an array equal to a value is:

$array[key] = value;

In other programming language you can only provide integer as the key value for the array but in PHP you can also specify a string as the key. This later type is referred to as Associative array

PHP arrays are mostly used with loops, which we will be discussing soon.

In PHP you have the following types of arrays:

Numeric array – An array with a numeric index
Associative array – An array where each ID key is associated with a value
Multidimensional array – An array containing one or more arrays

Numeric Arrays

A numeric array is the most common type of array, which stores each array element with a numeric index. This kind of array is found in all programming languages.

There are two methods to create a numeric array.

In the following example the index are automatically assigned (the index starts at 0)<$marks=array(20,10,30,40)
In the following example we assign the index manually:$marks[0]=20;
$ marks [1]=10;
$ marks[2]=30;
$ marks [3]=40;

Associative Arrays

In an associative array the key used is a string value. We have already seen how you can store the marks of the subjects you studied till now using an array. But there was a slight problem, you will not be able to distinguish which mark is for which subject unless you write it somewhere that which key value stands for which subject. This is extra information you will have to manage somewhere outside your program. Rather if there have been a way to store them together then it will lessen your burden.

Associative array is such a way. The key values of this array are strings.

$marks[“Physics”]=20;
$marks[“Chemistry”]=30;
$marks[“Biology”]=40;
$marks[“Maths”]=60;

Multidimensional Arrays

A multidimensional array is an array of arrays. In a multidimensional array, each element in the main array is also be an array. And each element in the sub-array can be an array, and so on.

$families = array (”Fruit”=>array (”Mango”,”Apple”,”Strawberry”),
“Animals”=>array (”Lion”,”Tiger”),
“Birds”=>array (”Eagle”,”Peacock”,”Penguin”)
);

The arrays and sub-arrays can be referred to as

$families['Fruit'][2] will refer to Strawberry.

Working with String variables

tutor — Fri, 11 Dec 2009 11:41:26 +0000

A string variable is used to store and manipulate character strings.

PHP provides some pre defined functions to manipulate string variables. There are someoperators also which directly work on strings.

For eg:

$txt=”Its PHP”;
echo $txt;
?>

Output:

Its PHP

We can use strings directly within double quotes or we can assign them to some variable and can use them through variables.

The Concatenation Operator

PHP provides an operator to manipulate string variables directly. This is called the concatenation operator represented by a “.” (dot).
The concatenation operator (.), as the name implies, concatenates two strings, ie it joins two or more strings.

For eg:

$txt1=”Its PHP!”;
$txt2=” So easy to use!”;
echo $txt1 . $txt2;
?>

Output:

Its PHP! So easy to use!

The strlen() function

Like in other languages PHP defines the strlen() function, which returns the length of a string.

For eg:

echo strlen(”Its PHP!”);
?>

Output:

This function can be useful in various string operations like matching two strings or finding some string in a large text where the loop counter should iterate till the last character of the text only. Various other applications can also use this function.

The strpos() function

The strpos() function searches a given character within a string.

If the character is found, this function will return the position of the first match. If no match is found, it will return FALSE.

For eg:

echo strpos(”Its PHP!”,”PHP”);
?>

Output:

The position of the string “world” is 6, as the counter starts from 0.

Using echo

tutor — Fri, 11 Dec 2009 10:33:57 +0000

As we used in previous pages, the PHP command echo is a way to uotput text to the web browser. Echo is the most commonly, and most ofetenly used command while working in PHP

We use echo to output a string. You can either use a variable or the string itself within quotes.

For eg:

$myString = “PHP”;
echo $myString;
echo “

PHP is too good!

”;
?>

Output:

PHP
PHP is too good!

The text that we output through echo is sent to the user in the form of a web page. So we can also use HTML tags inside the echo command,

Careful When Echoing Quotes!

It seems very good to be able to output HTML with PHP. However, you must be careful when using HTML code, when it contains quotes. Echo uses quotes to mark the beginning and end of the string, so you must not use quotes other than at the starting and the ending. If its necessary to use quotes inside echo you must use one of these methods

Use escape sequence to escape your quotes from echo ie just put a backslash directly before the quotation mark, like \”

Use single quotes (apostrophes) for quotes inside your string like ‘ ’.

Echo “

I Love PHP!

//doesn’t work
echo “

I love using PHP!

”; //works
?>

Echoing Variables

While echoing variables in PHP no quotations are required. They are written directly with echo as:

For eg:

$my_string = “PHP is too good ”;
$my_number = 4;
$my_letter = U;
echo $my_string;
echo $my_number;
echo $my_letter;
?>

Output:

PHP is too good 4U

Echoing Variables and Text Strings

You can also place variables inside of double-quoted strings. This tells the PHP interpreter to output the string value of the variable to be printed in the place of the variable.

For eg:

$my_string = “PHP is too good”;
echo “$my_string to use
”;
echo “PHP is a scripting language $my_string
”;
echo “PHP is a scripting language $my_string to use”;
?>

Output:

PHP is too good to use
PHP is a scripting language PHP is too good
PHP is a scripting language PHP is too good to use

Using variables saves time and provide reusability, you don’t need to retype the whole string over and again whenever you want to use it. With variables you can just use the variable whrever theres a need to use the same variable. It makes the code readable.

You should always use double quotes with string variables, as single quotes will not give the value of the string rather it will just print the variable name like

$my_string

PHP Variables

tutor — Fri, 11 Dec 2009 08:58:50 +0000

A variable is something whose value can be changing, or the other way round, a variable is used to store some values which are not constant. These values can be anything, like string, any integer value etc.

After declaring a variable you can use it again and again in your script.

Variables are declared using a $ sign. In PHP variables are typed according to the value they contain, so we don’t write any type specifier while declaring a variable.

$var_name = value;

If you forget putting a dollar sign before the name of a variable, it won’t work in PHP

PHP is a Loosely Typed Language.It internally converts a variable to the same type as the data type of its value. You can declare a variable only when you need one. No previous declaration is needed.

Naming Rules for Variables

PHP has variable declaration rules similar to other programming languages:

variable name can only start with a letter or an underscore “_”
variable name can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9, and _ )
variable name can not have spaces. If a variable name is of more than one word, it should be separated with an underscore, or with capitalization
like “$my_string” or “$myString”

Like other programming languages, variable names in PHP also are case-sensitive, so be sure to use the exact capitalization when using a variable. The variables $a_number and $A_number are different variables in PHP.

White Space

Like HTML, whitespaces are ignored in PHP. You can put any number of whitespaces may be to properly indent your code, and all the whitespaces will be ignored by the PHP interpreter.

Embedding PHP in HTML

tutor — Fri, 11 Dec 2009 07:54:58 +0000

PHP is almost always used with HTML. PHP scripts are embedded inside HTML pages anywhere in the body section.

A simple HTML page with PHP scripts looks like this:

Embedding PHP in HTML

echo ”It’s so good to be here!!!”;
?>

Output:

It’s so good to be here!!!

Echo is a PHP command to output string on the web page.
Echo is a vast topic so we will be discussing it later in this tutorial.

The Semicolon

Each line of PHP code ends with a semicolon. Semicolon is the PHP delimiter.

PHP will show an error if the semicolon is missed in any line.

echo ”It’s so good to be here!!!”;