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Use of PHP array variables for PHP newbies_PHP tutorial
- WBOYOriginal
- 2016-07-20 10:57:441119browse
PHPAfter a long period of development, many users know PHP very well. Here I will express my personal understanding and discuss it with everyone. You may be tired of spending a lot of time browsing the external landscape of PHP (learning all about PHP's control structures, operators, and variables). You might even consider quitting the tutorial right away, preferring (or so you would think) to spend your time in front of the TV.
If so, that would be a big mistake. And when I say "big," I mean huge. You see, if you give up on this chapter of the tutorial because of Ally McBeal's charm, you'll be missing out on one of PHP's coolest variable types. It's a little thing called an "array", and I'm not exaggerating when I tell you that once you get used to its usage, you'll look at PHP scripts in a different light. But don’t take my words as…, put those aside and try it out for yourself! As of now, the variables we’ve discussed only contain a single value, as shown in the code below
<ol class="dp-c"><li class="alt"><span><span><?php </span><span class="vars">$i</span><span> = 5; ?> </span></span></li></ol>
However, array variables are a completely different situation. Arrays are a complex variable type that allow you to store multiple values in a single variable (which makes it easy when you need to store and describe related information). We can think of PHP array variables as "container" variables that can hold one or more values. For example:
<ol class="dp-c">
<li class="alt"><span><span><?php </span><span class="comment">// define an array $pizzaToppings = array('onion', 'tomato', 'cheese'</span><span> </span></span></li></ol>Here, $pizzaToppings is an array variable that contains the values of 'onion', 'tomato', 'cheese', 'anchorvies', 'ham' and 'pepperoni' (array variable Especially useful for grouping related values). Print_r() is a special function that allows you to peek at the values inside PHP array variables. It's more useful for program debugging (finding out why a script is failing) than for displaying the contents of an array, but I'll use it here so you can understand what's going on beneath the surface. Make sure you have your server running and your browser open, okay?
Different elements in the array are accessed by index value, and the index of the first element starts from 0. So, to access the element 'onion', you would use the notation $pizzaToppings[0], while 'anchovies' would be $pizzaToppings[3] (essentially the array variable name followed by the index value enclosed in square brackets).
PHP also allows you to use user-defined "keywords" instead of indexes, in order to create a slightly different type of array. where each key is unique and corresponds to a single value in the array.
<ol class="dp-c"><li class="alt"><span><span><?php </span><span class="comment">// define an array $fruits = array('red' => 'apple', 'yellow' => 'banana', 'purple' => </span><span> </span></span></li>
<li>
<span class="string">'plum'</span><span>, </span><span class="string">'green'</span><span> => </span><span class="string">'grape'</span><span>); print_r(</span><span class="vars">$fruits</span><span>); ?> </span>
</li>
</ol>
In this example, $fruits is a PHP array variable containing four keyword-value pairs. (The => symbol is used to indicate the association between a keyword and its corresponding value). To access the 'banana' value, you use the $fruits['yellow'] symbol, while the 'grape' value is accessed via the symbol $fruits['green'].
Arrays of this type are sometimes called "hash arrays" or "associative arrays". If you have ever used Perl, you will see that it is similar to hash variables in Perl.
I hope this article’s introduction to PHP array variables can bring you some help.