How to add an array element to an array in php

Methods to add elements: 1. Use the "array_unshift(array, array element)" statement to add elements at the beginning of the array; 2. Use the "array_push(array, array element)" statement to add elements to the end of the array Add elements; 3. Use the "array_pad(array, array length 1, element)" statement.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

php adds to the array Methods of an array element

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);
var_dump($arr);
?>

array_unshift() function will not maintain the original numerical index relationship and will delete all Numeric key names are reassigned, that is, counting starts from 0; but all string key names 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);
var_dump($arr);
?>

array_push() function is different from array_unshift() function, it will not reset the value 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).

You only need to set the $size parameter to The original array length is 1 to insert a new element

<?php
$arr=array(10,12,20);
$result =array_pad($arr,4,1);
var_dump($result);
?>

From the above example, you can It can be seen that 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 beginning of the array; and the key to this 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.

<?php
header("Content-type:text/html;charset=utf-8");
$arr=array(10,12,20);
$result =array_pad($arr,-5,array("张三",25,"男"));
var_dump($result);
?>

The output result is:

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