What are the common array construction/value manipulation functions in PHP and their usage? (code)

The php array function is a very important part of php. The php array is composed of keys and values ​​corresponding to keys. The value of the corresponding key is accessed through the key of the element. Next, I will introduce to you the common array construction/value operation functions in PHP.

Associative array" refers to an array with a key name of a string. Index and key name have the same meaning in an associative array. "Index" can be understood as the numeric subscript of the array. Use the array processing function It is convenient to operate on the key and value of each element in the array, and then generate a new array.

1. PHP array function array_values()

The function array_values() is to return an array The values ​​of all elements in the array. It is simple to use. You only need to set a required parameter, specify the input array, and return an array of all the values ​​​​in the given array. The key names are not retained, and the returned array will be reconstructed using the sequential values. Create an index, starting from 0 and incrementing by 1. It is suitable for arrays with confusing array subscripts, or you can convert an associative array into an index array. The following figure is a simple example and running results.

<?php
$contact = array(
"ID" => 1,
"姓名" => "某某",
"公司" => "php中文网",
"地址" => "h市",
"电话" => "123456"
);
 
//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
?>

Running results:

Array([0]=>1 [1]=>XX[2]=>php Chinese website[3]=>h city[4]=>123456
Array ([ID]=>1 [Name]=>XX [Company]=>php Chinese website [Address]=> h City [Telephone]=>123456

2 , PHP array function array_keys()

The function array_keys() is to return all key names in the array. The function has one required parameter and two optional parameters, as shown in the figure below, $test is required Select parameters. If there are only required parameters, all key names of the array will be returned. Specifying the second parameter (Zhang San) will return the key name of the value. The function of the second optional parameter is to perform congruent comparison. You can use strict parameter if If the strict parameter is specified as true, PHP will use equality comparison (===) to strictly check the data type of the key value.

3. PHP array function in_array()

The function in_array() is to check whether a certain value exists in the array and search for it in the array. a certain value. The function has three parameters, the first two are required and the last one is optional.

The first parameter ("Zhang San") specifies the value to be searched in the array, and the second parameter ("$people") specifies the array to be searched , if the given value ("Zhang San") exists in the array ("$$people"), it returns TRUE. If the third parameter is set to TRUE, the function only returns TRUE if the given value ("Zhang San") exists in the array ("$ people") are the same, otherwise it returns FALSE. ("Zhang San") parameter is a string, and the third parameter is set to TRUE, the search is case-sensitive.

4. PHP array function array_filp()

The function array_filp() is used to exchange keys and values ​​in the array. In the returned array, if a value appears multiple times, the last key name will be used as its value, overwriting the previous elements. If the data type of the value in the original array is not string or integer, the function will report an error. The function has only one parameter. The following figure is a simple example:

<?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)
?>

5. PHP array function array_reverse()

The function array_reverse() is to reverse the order of elements in the original array and create a new one. The array is returned. There are two parameters, the first is a required parameter, the second optional parameter, if specified as TRUE, the key name of the element remains unchanged, otherwise the key name will be lost.

<?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)
?>

The above are commonly used array key/value operation functions. We will introduce them here first, which are all basic knowledge.

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