PHP study notes <1>

The blogger has written PHP for a period of time before, but the overall feeling was that it was to complete a specific function. He did not go into the syntax too much and was not familiar with many PHP functions. Therefore, today I will make a brief summary of these things~ (I will not write all the ways, I will only use the most common and concise way)

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Array Chapter

After preliminary reading of PHP arrays, I feel that this is actually Far beyond the scope of arrays. I feel that PHP arrays have some characteristics of vector+map in C++ STL. Even this is not enough to summarize its capabilities. Its built-in functions can add or remove elements from the head of the array and add and remove elements from the tail. You can determine unique array elements, count the occurrence frequency of arrays, and sort arrays. Even merge arrays, or make the values ​​of one array the keys of another, or split it. You can also find intersections, difference sets, or return several random values, or you can "shuffle" the cards.
This is completely different from the C++ and Java I have come into contact with before. Arrays bear the majority of PHP data structures. . In other words, the language itself has very few data structures at all?

If you want to see all the functions, go here.
Let’s start with the most basic one that best matches the characteristics of arrays
key is a number

<code><span>$state</span>=<span>array</span>(<span>0</span>=><span>"Alabama"</span>,<span>1</span>=><span>"Alaska"</span>,<span>2</span>=><span>"Wyoming"</span>);
当然这样也可以<span>$state</span>=<span>array</span>(<span>"Alabama"</span>,<span>"Alaska"</span>,<span>"Wyoming"</span>);</code>

key is a string

<code><span>$state</span>=<span>array</span>(<span>"English"</span>=><span>"s"</span>,<span>"Spanish"</span>=><span>"p"</span>);</code>

two-dimensional array
There is no two-dimensional array in PHP, but it can be implemented this way.

<code><span>$ps</span>=<span>array</span>(<span>array</span>(<span>1</span>,<span>2</span>,<span>3</span>),<span>array</span>(<span>4</span>,<span>5</span>,<span>6</span>),<span>array</span>(<span>7</span>,<span>8</span>,<span>9</span>));</code>

Special case: application of list
I have never seen this usage in other languages.
list(variable 1, variable 2, variable 3)=array(1,2,3);
This is equivalent to assigning values ​​to three variables separately.

Generate an array, filled with predefined values
I don't think this thing is very necessary, because the for loop will not be more complicated than it.

<code><span>$die</span>=range(<span>0</span>,<span>6</span>);
<span>$even</span>=range(<span>0</span>,<span>20</span>,<span>2</span>);
<span>$letters</span>=range(<span>"A"</span>,<span>"F"</span>);</code>

Test Array
Is it an array?

<code>bool is_array(<span>$state</span>);</code>

Print array
In addition to the for loop, there is a more convenient way to locate array elements

<code>boolean print_r(<span>$state</span>);</code>

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The above introduces the PHP learning notes , including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.