Understanding Arrays and How to Use Them
So in a recent project I have just finished up (again, will let you guys know what it is when it’s officialy released), arrays had become my best friend along with some regex, but that’s a topic for another post. I needed to turn strings into arrays, which I would then put back into arrays, and finally back into strings. I did this in a few different ways, but let’s go into some examples of why one would need to do this, then we’ll begin the how; seeing as the how without the why makes very little sense.
Well, I mainly use all this to transfer large amounts of separated data from function to function. In my most recent endeavor it was to split a specific type of file, parse it through 3 different functions (each function returned an array, but dealt with the data in strings which I will explain) then finally took all the information in the provided array and successfully dumped the data to a database. This is only one of the numerous reasons a person could/would use an array, but they help like one couldn’t imagine.
Let’s begin with the basics. For sake of example, we’ll keep things in PHP. The first example below just explains an array. No more, no less.
<?php
// Ways to add data to arrays!
$array1 = array("Entry 0","Entry 1","Entry 2","Entry 3"); // Just put data in
$array2 = array(
0 => "Entry 0",
2 => "Entry 2",
1 => "Entry 1"
); // Define arrays by opening and stating index.
$array3[0] = "Entry 0";
$array3[1] = "Entry 1"; // Enter directly into index?>
Another way to build an array, more or less indirectly, is to use php’s “explode();” function. This will take text with a defined delimiter and separate each set of data (at the delimiter) into its own index. For example, consider the following.
<?php
$string = "This is a string where we will, use commas, for delimiting the text and to, split this into an, array!";
$array = explode(",",$string);
print "Original: ".$string."<br /><pre>Array: ";
print_r($array);
print "</pre>";
?>
To call these defined arrays we would use $array[INDEX]. Now, there are many ways to access this data and filter it. Let’s begin by calling one value from an array.
<?php
$array = ("Entry 0","Use this text","Entry 2","Entry 3","This text isn't being called either");
print $array[1];
?>
The script above with print “Use this text” because it is in the array at the index value 1. It is important to remember that indexes start at 0 unless defined otherwise. Now, we’ll explain some more intricate ways of getting all your values. The first way is iteration using the “for();” loop. Here goes:
<?php
$array = ("Test","Test2","Word3","Keep 'em coming!","white space next","","No need for that","We <3 trim");
// Iterate.
for($i=0;$i<count($array);$i++){
print $i.") ".$array[$i]."<br />";
}
?>
Now this will just result similarly to the foreach(); which I am about to explain. However, sometimes iteration is more effective than foreach(); because it gives you more liberty. Most of the time I would recommend iteration for multi-dimensional arrays (arrays within arrays and so on), but usually two different ones. For example:
<?php
$array = array(array("Array in index","number 0"),array("Array in index","number 2"));for($i=0;$i<count($array);$i++){
// Now, let's get our multidimensional values!
for($ii=0;$ii<count($array);$ii++){
print "[".$i."][".$ii."]: ".$array[$i][$ii]."<br />";
}
}
?>
Now, that will grab all the data within the arrays within the arrays. Wow, sounds confusing, but once you get a better grasp, it’s really quite simple, but I cannot lie; it all seems very daunting at first. Now we’ll explain the foreach(); function. This function basically does what we just did manually, but sometimes is easier and more effective. A lot of times, you will use the two in conjunction (even if for different purposes), so become friendly with both of them!
<?php
$array = array(
0 => "Entry 0",
1 => "Another entry",
2 => "Again...",
3 => "And finally
);foreach($array as $key => $value){
print "Key/Index: ".$key.": ".$value."<br />";
}
?>
From the code above, you can see that the foreach(); function has accomplished the same feat we did earlier with iteration. On a simple array such as this, it would be best to use foreach, but like I said: it may be necessary at times to use iteration.
As I mentioned earlier, both can be used in conjunction. Just a quick example (we won’t go through the actual coding of it) is if you have a multi-dimensional array where you feel the need to use foreach, you can use foreach($var[$i] as $key => $val){} and work it that way.
So all in all, everything boils down to: love iteration, love foreach(); on the programming languages it’s available, and above all LOVE arrays! They are right next to regex in the developer’s “most useful tools” section of his or her tool belt!
Regards,
Dennis M.
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