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PHP is a popular, reliable programming language at the foundation of many smart, data-driven websites. This comprehensive course from Kevin Skoglund helps developers learn the basics of PHP (including variables, logical expressions, loops, and functions), understand how to connect PHP to a MySQL database, and gain experience developing a complete web application with site navigation, form validation, and a password-protected admin area. Kevin also covers the basic CRUD routines for updating a database, debugging techniques, and usable user interfaces. Along the way, he provides practical advice, offers examples of best practices, and demonstrates refactoring techniques to improve existing code.
PHP has another type of array, called an associative array. And it's important for us to learn how to use both types, and to understand the difference between them. An associative array is an object-indexed collection of objects and it's very similar to what we saw for the definition of a regular array. But notice that it doesn't say that it's ordered anymore. And instead of being integer-indexed it is object-indexed, that is, they're going to be indexed by a label of some sort. Let's remember the expanding file folder metaphor that I gave you when we were talking about arrays. Associative arrays are similar, but they work more like hanging file folders. They're not in any certain order and they can be rearranged. Each of those file folders is going to have a label on it. And that's how we're going to find information.
Since we won't know what order the information is in, instead we will thumb through those file folders until we find label that matches what we're looking for. Instead of saying, our phone bill is in pocket 1, and our electric bill is in pocket 2, instead we'll say, find the pocket labeled phone bill and pull out its contents. We call the label on each of these pockets the key, and the contents of what's inside the pocket the value. And the combination of the label and the value is referred to as the key value pair. So we'll always have a series of keys and values that make up our associative array.
Both an array and associative array have their uses. When the order matters to us we want to use an array. When the order is not important, we want to have the convenience of having a label that we can refer to, well then we want to use an associative array. So if we have 100 customers, we would want to store them in an array. The order of those customers is what matters. But then the information about each customer, I would want to store in an associative of array. I don't care that the first item in the array is their first name. In fact, I don't want to have to remember the order in which the data is stored. Instead I want to be able to ask the array, give me back the information that's labelled first name, and retrieve the data that I'm looking for. So both of them are going to have their place.
Let's try one out. So for associative arrays, let's start by opening up basic.html, we'll do Save As. We'll call this assoc_arrays. Assoc is what I'm going to use for short for association. Then make sure you put .php at the end. And here, associative arrays. Alright. Now, the function that we're going to use to create these is going to be exactly the same as what we had for our regular array. We're just going to use array with the parenthesis around it.
That is an empty associative array, as well as it is a regular array. There's really not a big difference. What matters though, is what we put inside of it. So, if for example, inside this array, I put first name as a label, that's a string, an object, it's object-indexed. And I point that and I do that using the equal sign and the greater than sign. So it looks like an arrow pointing to the next data, which is the value. So the key is first name, the value is Kevin. And we can have more than one of those. We can have comma and then last name.
Again, the arrow pointing to Skoglund, and you can put your own name in there instead of mine. There we go. That is what an associative array looks like. Instead of being indexed by the position, it's going to be indexed by the key. So if I wanted to get back the first name, (SOUND) echo, then I would do it by saying variable assoc square brackets still. Still asking for the value using square brackets, and now I need to put the index in here. Still an index. Before it was an index that was a position, now it's an index that's an object, and the object is the string first name.
Has to match exactly because that's the label. I'm looking for first name with that exact capitalization with the underscore in between them. Let's just put a br tag at the end of that. And let's bring that up in a browser. Instead of just arrays let's put assoc underscore in front of it. And there we go. It brought back the first name for us. It looked it up in our array based on its label. That's what it was indexed by. And of course, if we wanted to bring up both first name and last name, we know how to do that using a pen. I'll put a space, and then I'll just copy this, paste it here and turn this into last name. Bring that up, and you'll see that it brings back both values. Now assignment works the exact same way that it did when we were working with regular arrays.
We have assoc and then first name equals Larry. That's going to assign Larry to the thing that's labeled, that's indexed by first name, and then let's just echo it again, so that we can see the results. You can see now it's changed it and the value is equal to Larry in there. Now numbers don't work anymore. So for example, if we were to come down here and we were to ask it for what is in position 0, and let's bring that up.
You say it comes back and says oops, undefined offset. Right, basically I don't have an index called zero. I'm looking for zero and I don't see it there. So that's not going to work. That is unless you indexed it by using numbers. Right? Any number can be there, it doesn't have to be a string. We could use a number. So, in fact, what you'll realize is that this array that we had numbers, 4, 8, 15, 16, 23, and 42 is exactly the same as if we had this associative array written out. 0 points to 4, 1 points to 8, and so on. It's the exact same thing.
Let's just bring that up in a browser. And you can see that it brought up 4 for us. It returned this value because it's indexed with this. So, in fact, there's not a lot of difference between an array and an associative array, except that we have the convenience of not putting each one of those numbers in there, when we're just concerned about the order. So, you can see that, in fact, an array, an associative array, actually have a lot in common. They're really built the same way inside PHP. It's just that when we write it in this form, we aren't providing the indexes, we're assuming that it can be derived from the position of the items.
Whereas here, we're actually specifying what each one is. And if we wanted to make this one into 20, that's perfectly valid. We can do that. We can say that the index of it would be 20. It's not two anymore, it's 20. So arrays are going to play a big part in programming. So it's important that you make sure that you understand them. If this didn't make sense at first, then watch these two movies again and make sure that you have a good foundation on what they are and how they work before we move on. After that, we'll go to the next movie where we'll look at some functions that work on arrays.
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