PHP Programming Tips

PHP – Single vs. Double Quotes (Part 2)

Single quotes are used to define a set of characters and double quotes for variables, and as said the two are not inter-changeable and PHP will not check for a variable within single quotes. Below is a faster way of doing the same script with the simple substitution of the double for the single quotes.

Example:
$myword = ‘PHP is Free’;
if ($myword == ‘PHP is Free’)
{
echo ‘Learn it Easy’;}

The changes might be very minimal but for a serious scripting author, speed is of the essence and slow web pages are quite annoying.  As a web user like you and me should know, the faster a page opens, the better and the more we like it.

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Array_diff_assoc and array_diff_key Functions

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)

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Array Combine

This function combines two arrays where the first array is treated as the key and the second array as the contents of the said table. The syntax goes like this : array_combine(array1,array2), wherein the array1 is the table which contains the keys values, and the array2 is the contents. It should be noted that these two tables or array�s should have equal amounts of contents for it would become problematic if there was an error in the combination process. An example of the process is shown below:

$a1=array('a','b','c','d')
$a2=array2("Mouse","Rat","Rodent","Mice")
print_r(array_combine($a1,$a2))
?>

The output of which would give us a single table :

Array ( [a] => Mouse [b] => Rat [c] => Rodent [d] => Mice )

The function combined the two tables giving a single table that combines the keys and the contents. More in-depth discussion on the different array functions which in future posts would be the backbone of applications we will be building.

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Dissecting/Understanding the first program

The first post had you making a program that was equivalent to the “Hello World” program used for teaching basics of a programming language and here’s how it worked. When the script was requested by opening the web page, Apache intercepted the request and passed it onto PHP which parsed the script looking for the code in between the terminators and then doing the requested operation which was to display the text contained within the echo command. This result was given back to the server then again to the client. The output contained a valid HTML so the browser was able to understand it and execute the requested operation.

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