A detailed discussion on the use of PHP array variables_PHP tutorial

After a long period of development of PHP, 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.

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<span><strong><font color="#006699"><span class="tag"><?</SPAN><SPAN class=tag-name>php</SPAN></FONT></STRONG><SPAN> $</SPAN><SPAN class=attribute><FONT color=#ff0000>i</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>5</FONT></SPAN><SPAN>; </SPAN><SPAN class=tag><STRONG><FONT color=#006699>?></span></font></strong></span><span> </span>
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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:

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<span><strong><font color="#006699"><span class="tag"><?</SPAN><SPAN class=tag-name>php</SPAN></FONT></STRONG><SPAN> // define an array $</SPAN><SPAN class=attribute><FONT color=#ff0000>pizzaToppings</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>array</FONT></SPAN><SPAN>('onion', 'tomato', 'cheese', 'anchovies', 'ham', 'pepperoni'); print_r($pizzaToppings); </SPAN><SPAN class=tag><STRONG><FONT color=#006699>?></span></font></strong></span><span> </span>
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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, with the index of the first element starting 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.

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<li class="alt"><span><span class="tag"><?</SPAN><SPAN class=tag-name>php</SPAN><SPAN> // define an array $</SPAN><SPAN class=attribute>fruits</SPAN><SPAN> = </SPAN><SPAN class=attribute-value>array</SPAN><SPAN>('red' =</SPAN><SPAN class=tag>></span><span> 'apple', 'yellow' =</span><span class="tag">></span><span> 'banana', 'purple' =</span><span class="tag">></span><span> </span></span></li>
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<span>'plum', 'green' =</span><span class="tag">></span><span> 'grape'); print_r($fruits); </span><span class="tag">?></span><span> </span>
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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.