How to add and delete elements to php array

Add method: 1. array_unshift() inserts elements at the beginning, the syntax is "array_unshift(array, element list)"; 2. array_push() inserts elements at the end, the syntax is "array_push(array, element)". Deletion method: 1. array_shift() deletes the first element, the syntax is "array_shift(array)"; 2. array_pop() deletes the last element, the syntax is "array_pop(array)".

The operating environment of this tutorial: windows7 system, PHP8.1 version, DELL G3 computer

php array adding elements Method

1. The array_unshift() function inserts new elements into the array

##array_unshift($array,$value1,$ value2...)The function can insert one or more new elements (key values) at the beginning of the array.

Let’s take a closer look at the following example:

<?php
$arr=array(10,12,20);
array_unshift($arr,8,"9");
var_dump($arr);
?>

array_unshift($arr,8,9)It can be seen that two characters are inserted at the beginning of the $arr array new elements: the value "8" and the string "9", so the output result is:

array_unshift() The function will not maintain the original numerical index relationship, but will delete all numerical key names and reassign them, that is, count again from 0; but all string key names will remain unchanged.

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array("a"=>"red","b"=>"green",3=>"pink");
echo "原来的数组：";
var_dump($arr);
array_unshift($arr,"blue");
echo "在开头插入一个新元素后：";
var_dump($arr);
?>

Output result:

2. The array_push() function inserts new elements into the array

array_push($array,$value1,$value2...)The function can insert one or more elements (key values) at the end of the array.

Let’s take a closer look at the following example:

<?php
$arr=array(10,12,20);
array_push($arr,8,"9",3.14);
var_dump($arr);
?>

array_push($arr,8,"9",3.14)It can be seen that in the $arr array Insert 3 elements at the end: integer "8", string "9" and floating point number "3.14", so the output result is:

The array_push() function is different from the array_unshift() function. It does not reset the numerical key name, but counts based on the original numerical key name.

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array("a"=>"red","b"=>"green",3=>"pink");
array_push($arr,8,"9",3.14);
var_dump($arr);
?>

Output result:

3. The array_pad() function inserts new elements into the array

array_pad($array,$size,$value)The function can insert a key value $value into the array $array, thereby filling the array to the specified The length of $size. (The $size parameter can be understood as the final number of elements in the array, that is, the length of the array after the insertion operation).

Let’s take a closer look at the following example:

<?php
$arr=array(10,12,20);
$result =array_pad($arr,5,1);
var_dump($result);
?>

As can be seen from

array_pad($arr,5,1), $size## The value of # is 5, then there are 5 elements in the array after the insertion operation; and there are 3 elements in the original array, then only 2 elements need to be inserted. And because the inserted value $value is 1, you only need to insert 2 elements with the value "1". Therefore, the output result is:

As can be seen from the above example, the array_pad() function can insert elements at the end of the array. In fact, the array_pad() function can also insert elements at the end of the array. Insert elements at the beginning; and the key is the

$size

parameter. The

$size

parameter has three values: if

is a positive number, elements will be inserted at the end of the array;

• If

is a negative number, insert the element at the beginning of the array;
If its absolute value is less than or equal to the length of the
• $array

  array, no element will be inserted. Insert operation.

  <?php
  $arr=array(10,12,20);
  $result =array_pad($arr,-5,1);
  var_dump($result);
  $result =array_pad($arr,3,1);
  var_dump($result);
  $result =array_pad($arr,2,1);
  var_dump($result);
  ?>

The output result is:

The value of parameter

$value

can also be an array, that is Insert an entire array, and the original array will become a two-dimensional array. <pre class='brush:php;toolbar:false;'>&lt;?php header(&quot;Content-type:text/html;charset=utf-8&quot;); $arr=array(10,12,20); $result =array_pad($arr,-5,array(&quot;张三&quot;,25,&quot;男&quot;)); var_dump($result); ?&gt;</pre>The output result is:

#4. The array_splice() function inserts new elements into the array

array_splice($array,$start,$length,$value)

The function is a powerful function that can be used to delete array elements, replace array elements, and also insert array elements (just set the parameters $length can be set to 0). When

$length=0

, then the parameter $start can specify the position (subscript) to start inserting, and the parameter $value can The insertion value can be specified (if there are multiple values, it needs to be set as an array). Let’s take a closer look at the following example:

<?php
header("Content-type:text/html;charset=utf-8");
$arr1=array(10,12,20);
array_splice($arr1,0,0,"1");
var_dump($arr1);

$arr2=array(10,12,20);
array_splice($arr2,0,0,array("1",25,"3"));
var_dump($arr2);
?>

The output result is:

从上例可以看出，当$start=0时，会将$value值按顺序的插入到数组开头。那么想要在数组末尾插入元素要怎么弄？

简单，将$start的值设置为“数组长度值”，即count($arr)即可。

<?php
header("Content-type:text/html;charset=utf-8");
$arr1=array(10,12,20);
array_splice($arr1,count($arr1),0,"1");
var_dump($arr1);

$arr2=array(10,12,20);
array_splice($arr2,count($arr2),0,array("1",25,"3"));
var_dump($arr2);
?>

输出结果为：

php数组删除元素的方法

1、array_shift()函数删除第一个元素

array_shift() 函数用于删除数组中的第一个元素，并返回被删除的元素。

注释：如果键名是数字的，所有元素都将获得新的键名，从 0 开始，并以 1 递增

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array(10,12,20,25,24);
echo "原数组：";
var_dump($arr);

array_shift($arr);

echo "删除后的数组：" ;
var_dump($arr);
?>

2、array_pop()函数删除最后一个元素

array_pop() 函数删除数组中的最后一个元素。

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array(10,12,20,25,24);
echo "原数组：";
var_dump($arr);

array_pop($arr);

echo "删除后的数组：" ;
var_dump($arr);
?>

3、array_unique()函数移除重复元素

array_unique() 函数用于移除数组中重复的值。如果两个或更多个数组值相同，只保留第一个值，其他的值被移除。

注释：被保留的数组将保持第一个数组项的键名类型。

array_unique(array,sortingtype)

参数	描述
array	必需。规定数组。
sortingtype	可选。规定排序类型。可能的值： SORT_STRING - 默认。把每一项作为字符串来处理。 SORT_REGULAR - 把每一项按常规顺序排列（Standard ASCII，不改变类型）。 SORT_NUMERIC - 把每一项作为数字来处理。 SORT_LOCALE_STRING - 把每一项作为字符串来处理，基于当前区域设置（可通过 setlocale() 进行更改）。

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array(1,2,3,4,4,2,6);
echo "原数组：";
var_dump($arr);

echo "删除重复值后：" ;
var_dump(array_unique($arr));
?>

4、array_splice()函数删除任意位置元素

array_splice()是一个强大的函数，有多重功能：可以插入数组元素、可以替换数组元素，当然也可以删除数组元素（毕竟array_splice()函数的本职工作是删除指定元素并用其它值取代）。

array_splice()函数可以从指定位置开始删除指定个数的元素。

array_splice($arr,$start)会删除从$start位置开始的所有元素删除。

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array(10,12,20,25,24);
echo "原数组：";
var_dump($arr);

echo "删除后的数组：" ;
array_splice($arr,2);
var_dump($arr);
?>

$start参数有三种取值情况：

• 为正数，那么从$start位置开始，往后删除；

• 为0，那么从第一个元素开始，往后删除；

• 为负数，则从距离 $arr 末端 -start 的位置开始，从后往前删除。例如 -2 意味着从数组的倒数第二个元素开始。

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array(10,12,20,25,24);
echo "原数组：";
var_dump($arr);

echo "删除后的数组：" ;
array_splice($arr,-2);
var_dump($arr);
?>

array_splice()函数是强大的，可以删除多个元素，也可只删除一个元素，那就需要给该函数指定一个$length参数（第三个参数），该参数用来规定删除的元素个数。

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array(10,12,20,25,24);
echo "原数组：";
var_dump($arr);

echo "删除后的数组：" ;
array_splice($arr,2,1);
var_dump($arr);
?>

$length参数也有三种取值情况：

• 为正数，那么就表示删除 length 个元素；

• 为负数，那么将删除从 start 开始，到数组末尾倒数 length 为止的所有元素；

• 如果省略，那么将删除从 start 开始，一直到数组末尾的所有元素。

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array(10,12,20,25,24);
echo "原数组：";
var_dump($arr);

echo "删除后的数组：" ;
array_splice($arr,2,-1);
var_dump($arr);
?>

$length参数还可以为0，那么就表示不删除元素，可以和该函数的第四个参数$value相配合，进行插入操作（这里就不做具体介绍了）。

5、unset()函数删除指定下标元素

unset()函数可以删除指定下标（键名）的一个数组元素

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
  $arr = array(0 => "a", 1 => "b", 2 => "c");
  echo "原数组：";
  var_dump($arr);
  echo "删除后的数组：" ;
  unset($arr[1]);
          //↑ 你想删除的key
  var_dump($arr);
?>

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