Summary of using php arrays, summary of php arrays_PHP tutorial

Summary of using php arrays, summary of php arrays

In PHP, arrays are divided into two categories: index arrays and associative arrays. The two can be used alone or mixed.

1. One-dimensional array

The definition of a one-dimensional array is also very simple. There are two commonly used methods:

1.1 Direct assignment

1:

<span id="lnum3">   3:</span><span> $dwqs[1] = "我的博客:<span>";</span></span>

<span id="lnum5">   5:</span><span> $dwqs[3] = "程序爱好者:<span>";</span></span>

<span id="lnum7">   7:</span><span> $dwqs[5] = "欢迎你的加入";</span>

        1.2 Array()构建数组

1:

<span id="lnum3">   3:</span><span> ?></span>

2. Multidimensional array

Taking associative array as an example

1:

<span id="lnum3">   3:</span><span>     <span>"编号"</span> => <span>array</span>(1,2,3),</span>

array(<span>"独立博客"</span>,<span>"CSDN"</span>,<span>"博客园"</span>),

array(<span>"www.ido321.com"</span>,<span>"blog.csdn.net/u011043843"</span>,<span>"www.cnblogs.com/ido321"</span>)  

2. Array traversal In PHP, there are three commonly used array traversal methods: 1. for loop 1:

<span id="lnum3">   3:</span><span>     <span>echo</span> <span>"$dwqs[i]<br/>"</span>;</span>

    2、foreach语句

1: //The first way

<span id="lnum3">   3:</span><span> <span>foreach</span>($dwqs <span>as</span> $value){</span>

;

<span id="lnum6">   6:</span><span>  </span>

<span id="lnum8">   8:</span><span> <?php</span>

<span id="lnum10">  10:</span><span>     <span>echo</span> $key.<span>"=>"</span>.$value;</span>

    3、while循环

1:

<span id="lnum3">   3:</span><span>     <span>echo</span> $key.<span>":"</span>.$value;</span>

3. Some array-related functions (use the print_r() function to output the array content)

PHP’s array function is very powerful and is one of the most commonly used data types. Its processing function also has powerful and efficient characteristics.

1. Array key/value operation function

1.1 Function array_values(): Returns the values ​​of all elements in the array. Just pass in the array name, do not retain the key name, and the returned array will be re-indexed starting from 0.

1:

"博客" => <span>"www.ido321.com"</span>,<span>"程序爱好者"</span> => <span>"QQ群：259280570"</span>);

<span id="lnum4">   4:</span><span> print_r(array_values($dwqs2));</span>

" "www.ido321.com","程序爱好者"=">" "qq群：259280570");<="" font="">

<span id="lnum7">   7:</span><span>  </span>

           1.2 函数array_keys()：返回数组中的键名。

1:

<span id="lnum3">   3:</span><span> print_r(array_keys($dwqs2)) </span>

<span id="lnum5">   5:</span><span> print_r(array_kays($dqws,<span>'ID'</span>));</span>

         1.3 函数In_array()：检测数组中是否存在某个值

1:

<span id="lnum3">   3:</span><span> <span>//输出：存在</span></span>

<span id="lnum5">   5:</span><span>     <span>echo</span> <span>"存在"</span>;</span>

<span id="lnum7">   7:</span><span> <span>else</span>{</span>

<span id="lnum9">   9:</span><span> }</span>

2. Number of arrays and uniqueness 2.1 Function count(): Count the number of elements in an array or the number of attributes in an object 1:

<span id="lnum3">   3:</span><span> ?></span>

2.2 Function array_unique(): Delete duplicate values ​​in the array, and the returned array key name remains unchanged

1:

'php',<span>'b'</span> => <span>'mysql'</span>,<span>'c'</span> => <span>'linux'</span>,<span>'d'</span> => <span>'php'</span>);

<span id="lnum4">   4:</span><span> print_r(array_unique($a));</span>

       2.3 函数array_count_values()：统计数组中所有值出现的次数，返回的数组以原数组中的值作为键名，键值则是元素在原数组中出现的次数

1:

<span id="lnum3">   3:</span><span> print_r(array_count_values($a));</span>

3. Array sorting


Source: http://www.ido321.com/596.html

How to use arrays in php classes?

If you define private $a; as public $a, you can use $obj->a directly.

$obj->a['key'] is the value you want to access.

Usage of php array

First of all, your way of writing is really different. Nowadays, PHP is more common in curly bracket writing

(1) For weak language PHP, it does not need to be initialized like a strict language. It is automatically initialized when used. . So after declaring the array, it can be used. And sometimes there is no need to declare it, such as writing $i = 1.25 directly; if an error is reported in a rigorous language, PHP can use it like this.
(2) The default index of the array starts from 0 and then increases by 1. count($arr) is the number of array elements. Assuming n is the number of elements in the current array, then $arr[n-1] is the element with the largest index. Adding $arr[n] is equivalent to adding an element at the end of the array. In fact, you can write $arr[] = $ss, and the effect is the same.
(3) Algorithm idea problem, which means that if a natural number can be divided by a smaller prime number than it, then it is not a prime number.
(4) There is nothing wrong with the program....

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