The Variable Naming standard you choose, can be anything you want, bearing in mind that different languages have restrictions on what can be used to name variables, and some keywords are banned from being included in variable names. Some languages are also case sensitive, or insensitive, and that also has as effect on variable names.

Variables in Php
The variable name is case-sensitive and starts with a letter or underscore, followed by any number of letters, numbers, or underscores.

Variable Naming Tips

1) Choose a standard, that comes naturally to you, and one that will adequate describe the variable and the use of the variable. Also insure that the naming standard you choose, if you are having multiple members on your team, that everyone sticks to the same standard.
$website_name = “Php Tutorial Site”;

2) Iteration and other loops, you can use the “known” variables that are associated with iterations
$ index;
$indx;
$ndx;
$n;
$i;
$count;
$counter;

While these variables do not appear descriptive, when it comes to loops, they describe the functionality very well, and that usage is commonly known in the programming world.

3) Using Upper and Lower Case
This helps in making the name of the variable easy to read, as it provided a break to the eyes, and help the programmer to understand that variable and it purpose. This helps to show the normal speak break that is associated when joining 2 or more words.

$fullname;
$FullName;
$myfirstbook;
$MyFirstBook;
$phptutorialsite;
$PhpTutorialSite;

4) Using the underscore is another way to join word, and provide the natural breaks, just as we did with the Upper and Lower Case, we can also use the _ underscore, in conjunction with the Upper and Lower Case to get full effect and making the variable names easy to use.

$mywebsitename=”Php Tutorial Site”
$my_website_name = “Php Tutorial Site”;
$MyWebsiteName = “Php Tutorial Site”
$My_Website_Name= “Php Tutorial Site”

Alogn with writing comments in your PHP program, having descriptive variable names is an effective technique in reducing the number of hours spent programming and debugging.

We just introduced functions, now along with functions comes Scope of variables. In common day terms, let me try to explain scope. If you have 4 tvs in different rooms, with 4 cables box. Then each tv can show a
different channel, however, if you have 4 tvs, and 3 cables boxes and 2 tvs sharing a cable box. Then you will only have 3 different shows. So that 2 tvs share the same show and the other 2 tvs, showing their own shows. That is how scope works..

Global Scope

Variable scope becomes important, when you have 2 variables with the same name, as can easily happen within large application. It also ocurrs when you write functions to perform specific tasks.

This means that no matter where you are in the programs code, this variable will be known and have the same value everywhere. So in our tv example, this means that all 4 tvs, are using the same cable box, so when you change a channel on any tv, all the other tvs will change channel as well.

Global variables, can be useful, but i have been taught, and i continue to believe, that where possible you should stay away from global variables. In most cases, they are different ways to getting around global variables, but other times, you just have to use them.

Local Scope

Variables defined in local scope are only available within they “block”, function in which they are defined. So outside of the function or block, these variables will have no value, and will be unknown.

Within the scope they are defined, if they happen to be defined in another scope, then changes made to the variable in one place will not affect what happens in the other function. Back to the tv scenario again, 2 cables box, no matter what you do with one box, unless you go and change the other box, the changes on the first box will not make a difference.

Static Variables

Variables declared in a function, are defined everytime a function is called. So that if the function is called and the variable is defined to be zero and the variable was modify to be 10,when the function is called a
second time, the variable goes back to being zero when the function is called.

Static variables defined in a function, remember the value of the variable, when it was modified and uses that value everytime the function is called. So in actual fact, a static variable within a function, always remember what it value is, so that when the function is called again, it just continues from where it left off, and does not start again from the declaration.

Examples Of Scope

< ?php

$index = 0;
$teacher = "Joe Pulie";

function print_names ($index, $newchild)
{

static $counter = 9;

if ( $newchild == "yes")
$counter++;

$teacher = "Juan Guinn";

print "\nMy teacher name is $teacher\n"."
“;

for ($index; $index< =$counter; $index++)
{
print "\nI am child $index out of $counter children\n"."
“;
}

global $teacher;

print “\nMy teacher name is $teacher\n”.”
“;

}

print “” .” \nHello Testing Scope\n”.”

“;
print_names($index,”no”);
$index = 9;
print “
“;
print_names(9,”yes”);
print “
“;
$bindex = 5;
print_names(5,”yes”);
print “
“;
?>

Hello Testing Scope

My teacher name is Juan Guinn
I am child 0 out of 9 children
I am child 1 out of 9 children
I am child 2 out of 9 children
I am child 3 out of 9 children
I am child 4 out of 9 children
I am child 5 out of 9 children
I am child 6 out of 9 children
I am child 7 out of 9 children
I am child 8 out of 9 children
I am child 9 out of 9 children
My teacher name is Joe Pulie

My teacher name is Juan Guinn
I am child 9 out of 10 children
I am child 10 out of 10 children
My teacher name is Joe Pulie

My teacher name is Juan Guinn
I am child 5 out of 11 children
I am child 6 out of 11 children
I am child 7 out of 11 children
I am child 8 out of 11 children
I am child 9 out of 11 children
I am child 10 out of 11 children
I am child 11 out of 11 children
My teacher name is Joe Pulie

Just is just touching the surface of scope, if you have any more questions, feel free to send me an email.

Functions are the robots of any programming languages and in PHP they just the same. They are mainly used to make code reusable and easy to read. If you need to record a show on television only one time, do you program the VCR? however, if you need to record the same show everday, you use the timer
and the programmer on the VCR to make it happen.

Use of Functions
You have been using functions all along in your PHP programming without actually calling them functions. So instead of having to enter the code over and over again, you just made a simple function call to the already defined function and one you went merrily.

The most important question to ask yourself when you are thinking about writing a function, is how many times am i gonna be using this same or reasonable same programming code to accomplish this task? Of if you see yourself having to use the code over and over again, then you need to put it in a function.

Example of a PreDefined Function
print( “I am a predefined function. yes i meaning PRINT”);

See now, I told you that you used functions all along. Behind the scenes there is code that tells print what to do with the information is it sent i.e, What information you want to have printed.

Syntax of Functions
A function, in simple terms takes input(argument(s)) and produces output(results(s)). The code within a function does operations on the inputs and then produces output.

Function Definition

function my_function ($agruement1, $agruement2, $agruement3)
{
return $fctval;
}

The above function, takes three parameters, and then returns a value. These parameters are passed by value,. Remember that for the future

function my_other_function ()
{
/* any valid php code. */
}

The above function, just does operations with no parameters, this can be used in many ways including writing output to the screen.

Function Calls

$returnedvalue = my_function($value1, $value2, $value3);

Since my_function returns a value, we can use it in any arithmetic function, just like we would use any other variable.

my_other_function();

Now that is just a basic introductions to functions, we will discuss functions in more details in a future tutorial.

We touched on these features in PHP before, now lets go a little deeper into the operation of these functions.

Examples

$index++; // Post-increment, Give the value of index, then increments index by one
++$index; // Pre-increment, increments index by one, then returns the valueof index
$index–; // Post-decrement, Give the value of index, then decreases index by one
–$index; // Pre-drecrement, decreased increments index by one, then returns the value of index

Coded Example

< ?php
echo "Post-increment";
$index = 10;
echo "Index value(10): " . $index++. "\n";
echo "Index value(11): " . $index . "\n";

echo "Pre-increment";
$index = 10;
echo "Index value(11): " . ++$index. "\n";
echo "Index value(11): " . $index . "\n";

echo "Post-decrement";
$index = 10;
echo "Index value(10): " . $index--. "\n";
echo "Index value(9): " . $index . "\n";

echo "

Pre-decrement”;
$index = 10;
echo “Index value(9): ” . –$index. “\n”;
echo “Index value(9): ” . $index . “\n”;

?>

This little features, can come in very hand, so always look for ways to simplify your code and make things easier for yourself

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