Easy PHP Programming

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)

PHP’s use is not limited to the programming language for open source or custom written application. Don’t you know that PHP is also constructive for commercial application distribution? But there’s a little disadvantage to PHP’s interpreted language because it implies that the source code you wrote is open for others’ view. But there is of course a technique called Obfuscation to not allow others see the code you have written. Iono and PHP Encoder (by IonCube) is an application used to obfuscate and license the code you wrote. Iono serves as a front end to your licensing and PHP Encoder secures the codes. In this way, you can still keep the codes for yourself.

The first function, array_diff() is used for comparing several tables or arrays which gives an array with the keys and values from the first array if the value is not available in the other arrays. Syntax is as follows : array_diff(array1,array2,array3……), where array 1 is the table to which all the other arrays will be compared to. The 2nd array(array 2) is an array that is compared with the first array and so on and so forth. Below is sample code of its use and the outcome of the functions comparison :

$a1=array(0=>“Mouse”,1=>”Cat”,2=>”Dog”);
$a2=array(3=>”Dog”,4=>”Cat”,5=>”Lizard”);
print_r(array_diff($a1,$a2));
?>

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

The array_count_values() function returns an array which contains the keys of the original array’s value and the value is the number of occurences. A sample of it’s use is shown below:

$a=array("Mouse","Cat","Dog","Cat");
print_r(array_count_values($a));
?>

Which would give us an output of : Array ( [Mouse]=> 1 [Cat]=> 2 [Dog]=> 1 )

The next functions are used to compare the contents of one array against one or more arrays either returning the key, keys and contents or solely the contents of the specified fields that result from their comparisons. They are array_diff(), array_diff_assoc(), array_diff_key(), array_diff_uassoc() and array_diff_ukey(). all of these are used to determine the difference between a set of arrays returning either the keys or contents to give the results of the said array comparison/s.

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.

As with all programming languages PHP has different variable types such as numeric, character, string and Boolean types. Boolean variables in PHP always return either true or false, integers are whole numbers, floating points are decimal or scientifically notated and strings are a chain of characters. Sounds familiar, well they are and they are mostly standard across the various programming languages. For a more in-depth discussion on the different data types of PHP go visit the manual page.
We next discuss operators such as the assignment operator which allows you to assign values to variables allowing complex operations to be constructed into more and more functional programs.

More than a quarter of all software vulnerabilities identified among the Common Vulnerabilities and Exposures (CVE) listed and recorded in the National Vulnerability Database is related to PHP. This makes PHP susceptible to hackers who develop scantily built applications written in PHP. Most of these vulnerabilities can be slightly exploited without being logged on the computer hosting the exposed application. Because of bad programming habits such as failing to check data before entering into a database, and certain features, such exploitation is possible.. This kind of attacks is not limited to PHP and can mostly be avoided by following the appropriate coding procedures and principles.

The major notable difference with PHP against other languages with regards to variables is that PHP is more “intelligent”. In C for example, variables have to be explicitly defined as either numeric or alpha-numeric and can only be used to store that defined specific form of data. PHP like all other languages supports a lot of variable types such as integers, floating point numbers, arrays and strings but with one major difference, variables are recognized automatically based on their use and the context of their use. This makes your (programmer’s) life a whole lot easier. PHP variables are defined with a “$” symbol preceding the variable name. It should also begin with either an underscore or an alpha character.

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.

As you might have seen, all of the PHP statement ends with �;� which would be somewhat similar to Perl. The valid HTML code that was handed back to the server was :



Who are You?

My name is MacGyver.

More in the coming posts when we dig deeper as we widen our understanding of PHP.