Detailed introduction to the basic concepts of PHP arrays in Treasure Chest

Detailed introduction to the basic concepts of PHP arrays in Treasure Chest_PHP Tutorial

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Release： 2016-07-15 13:27:09

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Arrays are very important in our PHP. How to use arrays to achieve the functions we want, let’s take a look at the basic knowledge about PHP arrays. We haven't been studying for a long time, but some members can't wait to implement many website functions. Haha, it's good to have such requirements and wishes. This is actually the driving force for our progress. However, as a programming language, we still need to master some basic rules, such as data types, syntax, etc.

Fortunately, PHP is not difficult, and there are not many of these things. After learning a few lessons, we can start to use it to implement website functions one by one. I believe you will become more energetic in time. Okay, let’s start today’s lesson. Today we are learning about arrays. Arrays are a data type that are used very frequently. Learning to handle arrays will make you more comfortable when building a website. For example: Your website database contains Dali articles. Now you want to display 20 entertainment news titles on one page. After these 20 titles are taken out from the database, do you want to use 20 variables to represent them? I don’t think you are that stupid, so what variables can be used to completely receive these 20 pieces of data? This requires the use of array variables.

What is an array? An array is actually a data collection, which is equivalent to a data container. A lot of data is stored in it. We can save it in or take it out according to certain methods. We can also sort the data in it and other operations. We can also check whether there is any data in it. There is no data we want and so on.

Definition of PHP array:

You can use the array() language structure to create a new array (array). It accepts a number of comma-separated key => value parameter pairs. For example 8-1:

<ol class="dp-xml">
<li class="alt">
<span><strong><font color="#006699"><span class="tag"><?</SPAN><SPAN class=tag-name>php</SPAN></FONT></STRONG><SPAN> </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute><FONT color=#ff0000>arr</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>array</FONT></SPAN><SPAN>(</SPAN><SPAN class=attribute><FONT color=#ff0000>1</FONT></SPAN><SPAN> =</SPAN><SPAN class=tag><STRONG><FONT color=#006699>></span></font></strong></span><span> "新浪", </span><span class="attribute"><font color="#ff0000">2</font></span><span> =</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>"网易", </span><span class="attribute"><font color="#ff0000">3</font></span><span> =</span><span class="tag"><strong><font color="#006699">></font></strong></span><span> "腾讯", "雅虎");  </span>
</li>
<li class="alt">
<span></span><span class="tag"><strong><font color="#006699">?></font></strong></span><span> </span>
</li>
</ol>

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The data in the array is actually arranged in a certain order. Each data has a key corresponding to it. This key (key value) is determined by yourself. If you have not given When the key is released, the system will assign a key value (key) in sequence. Here "Yahoo" we did not give a key value, but the system will assign it a key value of 4.

Since the system can automatically assign key values, is it possible not to write the key value? Of course you can. For example, you can write 8-2 like this:

<ol class="dp-xml"><li class="alt">
<span><strong><font color="#006699"><span class="tag"><?</SPAN><SPAN class=tag-name>php</SPAN></FONT></STRONG><SPAN> </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute><FONT color=#ff0000>arr</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>array</FONT></SPAN><SPAN>( "新浪", "网易", "腾讯", "雅虎");  </SPAN></SPAN><LI class=alt><SPAN> </SPAN><SPAN class=tag><STRONG><FONT color=#006699>?></span></font></strong></span><span> </span>
</li></ol>

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Note here: the system allocates key values starting from 0. Do you know what the key value of "Sina" is?

How to access PHP array data:

We have so much data above represented by the variable $arr, what should we do to get the data we want from it? For example, take the data in Example 8-1 and do 8-3:

<ol class="dp-xml">
<li class="alt">
<span><strong><font color="#006699"><span class="tag"><?</SPAN><SPAN class=tag-name>php</SPAN></FONT></STRONG><SPAN> </SPAN></SPAN><LI class=""><SPAN>   </SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute><FONT color=#ff0000>arr</FONT></SPAN><SPAN> = </SPAN><SPAN class=attribute-value><FONT color=#0000ff>array</FONT></SPAN><SPAN>(</SPAN><SPAN class=attribute><FONT color=#ff0000>1</FONT></SPAN><SPAN> =</SPAN><SPAN class=tag><STRONG><FONT color=#006699>></span></font></strong></span><span> "新浪", </span><span class="attribute"><font color="#ff0000">2</font></span><span> =</span><span class="tag"><strong><font color="#006699">></font></strong></span><span>"网易", </span><span class="attribute"><font color="#ff0000">3</font></span><span> =</span><span class="tag"><strong><font color="#006699">></font></strong></span><span> "腾讯", "雅虎");  </span>
</li>
<li class=""><span>   </span></li>
<li class="alt"><span>echo $arr[1];  //这个会输出“新浪”  </span></li>
<li class=""><span>echo $arr[2];  //这个会输出“网易”  </span></li>
<li class="alt"><span>echo $arr[3];  //这个会输出“腾讯”  </span></li>
<li class=""><span>echo $arr[4];  //这个会输出“雅虎”  </span></li>
<li class="alt"><span>   </span></li>
<li class="">
<span></span><span class="tag"><strong><font color="#006699">?></font></strong></span><span> </span>
</li>
</ol>

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is to use the variable name plus different keys in square brackets to access different data. We also call the key in the square brackets a subscript. What should I do to get the "Sina" in 8-2? By the way, use $arr[0].