Array key/value operation functions, array functions_PHP tutorial

Key/value operation function of array, array function

PHIn P, each element of the array is composed of key/value Composed, the value of the corresponding key is accessed through the key of the element. "Associative array" refers to an array with a string key name, and "index" and "key name" refer to the same thing. "index" The numeric subscript of a multi-exponent array. Using the array processing function, you can easily operate on the key and value of each element in the array to generate a new array.

①Function array_values()

The array_values() function is to return the values ​​of all elements in the array. It is very easy to use. There is only one required parameter, which specifies that the given array is passed in and an array containing all the values ​​in the given array is returned. But the key names are not preserved, and the returned array will be re-indexed using sequential numeric keys, starting at 0 and increasing by 1. It is suitable for arrays with chaotic elements in the array, or can convert associative arrays into indexed arrays. The code looks like this:

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<?php $contact = array( "ID" => 1, "姓名" => "高某", "公司" => "A公司", "地址" => "北京市", "电话" => "(010)98765432" );   //array_values()函数传入数组$contact 重新索引返回一个新数组   print_r(array_values($contact)); print_r($contact); //原数组$contact内容元素不变 ?>

The result after running the program is as follows:
Array([0]=>1 [1]=>Gao [2]=>Company A[3]=> Beijing[4]=>(010)98765432)
Array([ID]=>1 [Name]=>Gao [Company]=>Company A [Address] => Beijing [Tel] =>(010)98765432)

②Function array_keys()

The array_keys() function is to return all the key names in the array. This function has one required parameter and two optional parameters. The prototype of its function is as follows:

array array_keys(array input[,mixed search_value[,bool strict]])
If the optional parameter search_value is specified, only the key name of the specified value will be returned, otherwise the key name in the input array All key names will be returned. Since PHP5, you can use the strict parameter to perform congruent comparisons. A Boolean value needs to be passed in. FALSE is the default value and does not depend on the type. If a TRUE value is passed in, the key name with the specified value is returned according to the type. The code used by the function array_keys() is as follows:

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<?php $lamp = array("a"=>"Linux","b"=>"Apache","c"=>"MySQL","d"=>"php"); print_r(array_keys($lamp)); //输出Array([0]=>a [1]=>b [2]=>c) print_r(array_keys($lamp,"Apache")); //使用第二个可选参数输出：Array([0]=>b)   $a = array(10,20,30,"10"); //声明一个数组，其中元素的值有整数10和字符串"10" print_r(array_keys($a,"10",false)); //使用第三个参数(false)输出：Array([0]=>0 [1]=>3)   $a = array(10,20,30,"10"); //声明一个数组，其中元素的值有整数10和字符串"10" print_r(array_keys($a,"10",true)); //使用第三个参数(true)输出：Array([0]=>3)   ?>

③Function in_array()

The function of

in_array() function is to check whether a certain value exists in the array, that is, to search for a given value in the array. There are three parameters in this function, the first two parameters are required, and the last parameter is optional. The prototype of its function is as follows:

bool in_array(mixed needle,array haystack[,bool strict])

The first parameter needle specifies the value to be searched in the array, and the second parameter haystack specifies the array to be searched. If the given value needle exists in the array haystack, TRUE is returned. If the third parameter is set to TRUE, the function returns TRUE only if the element exists in the array and has the same data type as the given value. If the parameter is not found in the array, the function returns FALSE. Note that if the needle parameter is a string and the strict parameter is set to TRUE, the search is case-sensitive. The code used by the function array_keys() is as follows:

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<?php //in_array()函数的简单使用形式 $os = array("Mac","NT","Trix","Linux");   if(in_array("Trix",$os)){ //这个条件成立，字符串Trix在数组$os中 echo "Got Trix"; }   if(in_array("mac",$os)){ //这个条件失败，因为in_array()是区分大小写的 echo "Got mac"; }   //in_array严格类型检查例子 $a = array('1.10',12.4,1.13);   //第三个参数为true，所以字符串'12.4'和浮点数12.4类型不同 if (in_array('12.4',$a,true)){ echo "'12.4' found with strict checkn"; }   if (in_array(1.13,$a,true)){ //这个条件成立，执行下面的语句 echo "1.13 found with strict checkn"; }       <code class="php spaces"> //in_array()中还可以用数组当做第一个参数作为查询条件<code class="php comments">//in_array()中还可以用数组当做第一个参数作为查询条件     <code class="php spaces"> $a<code class="php variable">$a = <code class="php plain">= array<code class="php keyword">array(<code class="php plain">(array<code class="php keyword">array(<code class="php plain">('p'<code class="php string">'p',<code class="php plain">,'h'<code class="php string">'h'),<code class="php plain">),array<code class="php keyword">array(<code class="php plain">('p'<code class="php string">'p',<code class="php plain">,'r'<code class="php string">'r'),<code class="php plain">),'o'<code class="php string">'o');<code class="php plain">);       <code class="php spaces"> if<code class="php keyword">if(in_array(<code class="php plain">(in_array(array<code class="php keyword">array(<code class="php plain">('p'<code class="php string">'p',<code class="php plain">,'h'<code class="php string">'h'),<code class="php plain">),$a<code class="php variable">$a)){            <code class="php plain">)){ //数组array('p','h')在数组$a中存在<code class="php comments">//数组array('p','h')在数组$a中存在         <code class="php spaces"> echo<code class="php functions">echo "'ph'was foundn"<code class="php string">"'ph'was foundn";<code class="php plain">;     <code class="php spaces"> }<code class="php plain">}       <code class="php spaces"> if<code class="php keyword">if(in_array(<code class="php plain">(in_array(array<code class="php keyword">array(<code class="php plain">('h'<code class="php string">'h',<code class="php plain">,'p'<code class="php string">'p'),<code class="php plain">),$a<code class="php variable">$a)){            <code class="php plain">)){ //数组array('h','p')在数组$a中不存在<code class="php comments">//数组array('h','p')在数组$a中不存在         <code class="php spaces"> echo<code class="php functions">echo "'hp'was foundn"<code class="php string">"'hp'was foundn";<code class="php plain">;     <code class="php spaces"> }<code class="php plain">} ?>?>

You can also use the array_search() function to search. This function has the same parameters as in_array(). It searches for a given value and returns the corresponding key name if it exists. It also supports strict judgment on the data type. The code used by the function array_search() is as follows:

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<?php $lamp = array("a"=>"Linux","b"=>"Apache","c"=>"MySQL","d"=>"php");     echo array_search("php",$lamp);         //输出：d（在数组$lamp中，存在字符串"php"则输出下标d）       $a = array("a"=>"8","b"=>8,"c"=>"8");     echo array_search(8,$a,ture);           //输出b(严格按类型检索，整型8对应的下标b) ?>

In addition, using the array_key_exists() function you can also check whether a given key name or index exists in the array. Because the key name must be unique in an array, there is no need to judge its data type. You can also use the isset() function to check the key names in the array. Single isset() will not return TRUE for NULL values ​​in the array, but array_key_exists() will. The code looks like this:

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<?php $search_array = array('first'=>1,'second'=>4);            //声明一个关联数组，其中包含两个元素       if(array_key_exists('first',$search_arry)){             //检查下标为first对应的元素是否在数组中         echo "键名为'first'的元素在数组中";     }       $search_array = array('first'=> null,'second'=>4);            //声明一个关联数组，第二个元素的值为NULL       isset($search_array['first']);                  //用isset()检索下标为first的元素返回false     array_key_exists('first',$search_array);                //用array_key_exists()检索下标为first的元素返回true ?>

④Function array_flip()

The function of array_flip() is to exchange the keys and values ​​in the array. Returns a reversed array. If the same value appears multiple times, the last key name will be used as its value, overwriting the previous elements. If the value data type in the original array is not string or integer, the function will report an error. This function has only one parameter, and its function prototype is as follows:

array array_flip(trans)

The parameter is required and requires input of an array to be processed, and returns an array with the keys and values ​​of each element in the array exchanged. The code used by the function array_flip() is as follows:

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<?php $lamp = array("os"=>"linux","WebServer"=>"Apache","Database"=>"MySQL","Language"=>"PHP");       //输出：Array([linux]=>os [Apache]=>WebServer [MySQL]=>Database [PHP]=Language);     print_r(array_flip($lamp));             //使用array_flip()函数交换数组中的键和值       //在数组中如果元素的值相同，则使用array_flip()会发生冲突     $trans = array("a"=>1,"b"=>1,"c"=2);     print_r(array_flip($trans));            //现在$trans变成了：Array([1]=> b [2]=> c) ?>

⑤Function array_reverse()

The function of array_reverse() is to reverse the order of elements in the original array, create a new array and return it. This function has two parameters, and its function prototype is as follows:

array array_reverse(array array[,bool preserve_keys])

The first parameter is required and receives an array as input. The second parameter is optional. If TRUE is specified, the key name of the element remains unchanged, otherwise the key name will be lost. The code used by the function array_reverse() is as follows:

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<?php $lamp = array("OS"=>"Linux","WebServer"=>"Apache","Database"=>"MySQL","Language"=>"PHP");       //使用array_reverse()函数将数组$lamp中的元素的顺序翻转     print_r(array_reverse($lamp));     //输出的结果Array([Language]=>PHP [Database]=>MySQL [WebServer]=>Apache  [OS]=>Linux) ?>

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>> Fixed link to this article: http://php.ncong.com/php_course/arry_function/key-value.html

Read n from the keyboard Put the integers into the array, write the function CompactIntegers, delete all elements with a value of 0 in the array, and then add the elements to the array

#include
int Compactlntegers(int a[], int *m)
{
int i,j,n;//I used the C compiler to do it here, So I modified it a bit,
//If it’s C++, you should be able to use reference to pass value directly. According to what you originally wrote, you should be able to modify the value of n in the main program
n=*m;
for(i= 0;i {
if(a[i]==0)
{
for(j=i;ja[j ]=a[j+1];
n--;
}
}
*m=n;
return j;
}
void main()
{
int i,n,a[100];
printf("please input your number:\n");
scanf("%d",&n);
for( i=0;i {
printf("please input the %d number:",i+1);
scanf("%d",&(a[i] ));
}
Compactlntegers(a,&n);
for(i=0;i {
printf("the %d number is: %d \n",i+1, a[i]);
}
}

After the PHP array is shuffled using the shuffle function, duplicate values ​​appear in different keys

What about the code?
Does your array originally have duplicate values?

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