PHP Programming 101

Arrays are what tables are to C-based programming languages and what databases are for SQL-based languages. Arrays or tables as they are sometimes called can be used to store the contents of several variables and to create one, you use the following syntax:

Array(key=>value)

The array in the syntax refers to the name of the array being created, the key is the index which is set automatically to a numeric character or string if none is specified. Value is the assigned value or content of the said array which can be seen easily in the following array creation example:

$b=array('z'=>‘Comedy”,’y'=>”Horror”,’x;’=>”Action”);
print_r($b);
?>

This piece of code would produce an output of :

Array ([0] => Comedy [1] => Horror [2] => Action)

More on array functions in the next posts.

(cont….)

V. Operators in PHP

*Arithmetic Operators*

+ addition
- subtraction
* multiplication
/ division
% modulus (division remainder)
++ increment
– decrement

*Comparison Operators*
== equal to
!= not equal
> greater than
= greater than or equal
<= less than or equal

*Logical Operators*
&& and
|| or
! not

I know its self explanatory…

VI. IF….Else Statements

If (condition)
//*Things to be executed if the answer to the condition is true*//
else
//*Things to be executed if the answer to the condition is false*//

If…else statement is use if the user wants to execute a set of code when the condition is true and another if the condition is not true.

VII. Switch Statement

switch (expression)
{
case 1:
//*code to be executed*//
break;
case 2:
//*code to be executed*//
break;
default:
//*code to be executed*//
break;
}

Switch statement is use if you want to select one of many blocks of code to be executed. this statement is used to avoid long blocks of if…elseif..else.

VIII. Looping Statement

while(condition)
code to be executed;

While statement is used to execute a block of code if and as long as a condition is true

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

Do—while statement is used to execute a block of code at least once and it will repeat the loop as long as the condition is true.

for each (array as value)
{
code to be executed;
}

For each statement is used to loop through arrays.

I think this is already enough and it has added new knowledge to those who are new in PHP… good luck and happy coding…

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(cont…)
III. PHP Variables

$variablename=value;

Variables are used for storing values such as text string or arrays. And all variables in PHP starts with a ($) dollar sign. There are various rules to be follow before naming a variable. 1) A variable name must start with a letter or an underscore. 2) A variable name can only contain alpha-numeric characters and underscores. Special characters are not allowed. 3) A variable name should not contain spaces.

IV.PHP Strings

$wrd=”Hello World”;
print $wrd;

Strings variables are used for values that contain character strings. The only operator that can be used on string is concatenation denoted by the sign (.) period.

$wrd1=”Hello World”;
$wrd2=”Good day”;
print $wrd1.”".$wrd2

You can count the nos. of string with the function strlen().

Print strlen(”HelloWorld and GoodDay”);

to be continued…

image source: www.php-editors.com

Here are some of the basic things to be in mind while coding your dynamic web pages using PHP.

I. PHP basic syntax

PHP is a script that is place inside a HTML document that’s why you need to put the basic codes of HTML such as and .
PHP is open with the (?)question mark followed by “PHP” and closed with a (?) question mark.

II. Displaying in PHP

In order to display a text in PHP you need to use the keyword ECHO or PRINT. all code line ends with a semicolon.

To be continued…

image source: www.23hq.com

There are a lot of PHP scripts you can check out on the web. Some PHP scripts can even be downloaded and used on your own websites. Most of these scripts can be customized accordingly, but just make sure you save it as another file since in the event you have errors, you may find yourself having to revert to the original file.

You will be surprised at the number of scripts you can find on the web. A lot of them are good and others really basic. But the thing to get out of them is really the script design structure to which will help you learn. After seeing all of these, you will surely get yourself to write you very first PHP script to display on the Internet.

Next in line is array_diff_uassoc() function which compares two or more arrays while checking for differences before comparing the keys with a user-defined location. It then returns an array withthe keys and values from the first array(to which all the values were comapred against) it the function allows it. Syntax is as follows : array_diff_uassoc(array1,array2,array3….,function). with a sample below of how it is used.

function userdefined($v1,$v2)
{
if ($v1 === $v2)
{
return 0;
}
if ($v1 > $v2)
{
return 1;
}
else
{
return -1;
}
}
$a1=array(0=>”Dog”,1=>”Cat”,2=>”Horse”)
$a2=array(3=>”Dog”,1=>”Cat”,5=>”Horse”)
print_r(array_diff_uassoc($a1,$a2,”userdefined”));
?>

which results in the following output : Array( [0] => Dog [2] => Horse). For an example of the same function with two or more assigned arrays to the function:

function userdefined($v1,$v2)
{
if ($v1 === $v2)
{
return 0;
}
if ($v1 > $v2)
{
return 1;
}
else
{
return -1;
}
}
$a1=array(0=>”Dog”,1=>”Cat”,2=>”Horse”)
$a2=array(3=>”Dog”,1=>”Cat”,5=>”Horse”)
$a3=array(6=>”Onyx”,0=>”Dog”,5=>”Horse”)
print_r(array_diff_uassoc($a1,$a2,$a3,”userdefined”));
?>

Which in turn, gives you : Array ([2] => Horse )

So we see the different array_diff function variants and the diffeerent ways they are used to compare the values of one or more arrays with one another.

The next array comparison functions is the array_diff_assoc(array1,array2,array3,array3…..), usage is similar with all of these array_diff functions varying only in the way the comparisons are done. Below is sample code for array_diff_assoc:

$a1=array(0=>“Mouse”,1=>”Cat”,2=>”Dog”);
$a2=array(0=>”Lizard”,1=>”Dog”,2=>”Cat”);
$a3=array(0=>”Dog”,1=>”Cat”,2=>”Mouse”);
print_r(array_diff_assoc($a1,$a2,$a3))
?>

Giving you : Array ([0] => Mouse [2] => Dog).

Next we have the array_diff_key() function compares two or more arrays and returns an array with the keys and values from the first array only if the key is not present in the other arrays. Syntax is array_diff_key(array1,array2,array3……)which is similar to the other array_diff functions.

Sample usage:
$a1=array(0=>“Mouse”,1=>”Cat”,2=>”Dog”);
$a2=array(2=>”Fish”,3=>”Rat”,4=>”Bee”);
$a3=array(5=>”Dog”,6=>”Cat”,7=>”Fish”)
print_r(array_diff_key($a1,$a2,$a3));
?>

Giving you : Array([0] => Mouse [0] => Cat)

The array_chunk() function on the on the other hand as the name implies, divides an array into chunks or several tables from the source table. The syntax goes something like array_chunk(array,size,preserve_key), wherein the array is the table that would be divided, the size is the number of elements which the new arrays are to contain and the preserve key which can either be true or false is used to either retain or revise the key or pointer value of the original table. An example is shown below:

$a=array(�a�=>�Cat�, �b�=>�Dog�, �c�=>�Horse�,�d�=>�Cow�);
print_r(array_chunk($a,2);
?>

The code would have an output of:

Array (
[0] => Array ( [0] = > Cat [1] => Dog )
[1] => Array ( [0] => Horse [1] => Cow )
)

As we can see, the original array has been divided into two arrays array0 and array1 and a value that is not given for the key had it assigned a new key for each of the tables. Another example would be :

$a=array(�a�=>�Cat�, �b�=>�Dog�, �c�=>�Horse�,�d�=>�Cow�);
print_r(array_chunk($a,2,true);
?>

This would then give us ;
Array (
[0] => Array ( [a] = > Cat [b] => Dog )
[1] => Array ( [c] => Horse [d] => Cow )
)

This shows the significance of the retain key field wherein the two new arrays retained their original keys. The reverse of which would be the array_combine() which divided the array into one which holds the keys and one with the values.

This form of array declaration allows one to change the case from uppercase to lowercase and vice versa. The syntax goes as follows:

array_change_key_case(array,case)

The array part, specifies which table or array to use and is a required field which is not the case with the key which is automatically assigned a value. An example of it’s use can be seen below:

$a=array('a'=>“Mouse”,’b'=>”Rat”,’c'=>”Rodent”,’d'=>”Cat”);
print_r(array_change_key_case($a,CASE_UPPER));
?>

The output of the said commands will be:
Array ( [A] => Mouse [B] => Rat [C] => Rodent [D] => Cat)

Another example of it’s use would be:

$a=array('a'=>“Mouse”,’B'=>”Rat”,’c'=>”Rodent”,’b'=>”Cat”);
print_r(array_change_key_case($a,CASE_UPPER));
?>

That returns the following values respectively:
Array ( [A] => Mouse [B] => Rat [C] => Rodent [D] => Cat)

In the next post, we would discuss an array function that divides a large array into several chunks of separate arrays.

Now, to make you a better programmer we all know the value of comments. This allows you to understand the code that you have written defining and given meaning to operations as you build them up. You start with the terminators used by PHP and end with them as well. Single line comments look like this �// comment� and Multi-line ones use the syntax /* comment comment*/. A better example would be the one below:

//comment
/* comment
Comment*/
?>

In the next post we take on the best parts of PHP which would be variables which is essential in all programming languages.