PHP array learning: How to add elements to the beginning and end of the array?

In the previous article "How to delete the first and last elements in the array in PHP array operation? 》We introduced in detail how to delete the first element and the last element in the array elements in PHP. In this article, we will take a look at how to add elements to the beginning and end of the array. I hope Helpful to everyone!

In the previous article we learned that if we want to delete the first element in an array in PHP, we can use the array_shif function, think To delete the last element in the array, you can use the array_pop function. This article is going to learn exactly the opposite. Let's take a look at how to insert elements at the beginning of the array and how to insert elements at the end of the array.

In PHP, if you want to insert elements at the beginning and end of an array, you need to use the array_unshift function and the array_push function. Let's take a look at the use of these two functions separately.

<strong><span style="font-size: 20px;">array_unshift</span></strong>Function - Add elements at the beginning of the array

There is a built-in array_unshift function in PHP that can insert new elements at the beginning of the array. This is somewhat similar to array_shif but different. The basic syntax of the array_unshift function The format is as follows:

array_unshift(array,value1,value2,value3...)

What needs to be noted is:

The parameter array represents the array into which elements need to be inserted, and the parameter value123 represents the element to be inserted into the array array. If the function runs successfully, the returned result is the number of elements in the array.

When we use the array_shif function to delete an element, we can only delete one element, but when we use the array_unshift function to add elements at the beginning of the array, we can add multiple elements. If the key name in the array is a number, it will still be reassigned from 0, and the key name is a string will not be affected.

Let’s look at the use of the array_unshift function through an example. The example is as follows:

<?php
$a=array("a"=>"red","b"=>"green");
//返回结果的值
print_r(array_unshift($a,"blue"));
echo &#39;<br/>&#39;;
//添加新元素的新数组
print_r($a);
?>

Output result:

In the above example, we can see that when the program ends, the returned result is the number of new elements in the array, and the new element key names start from 0.

Let’s take a look at the changes in the output results of the elements with numeric key names in the original array. The example is as follows:

<?php
$a=array("a"=>"red","b"=>"green");
//返回结果的值
print_r(array_unshift($a,"blue"));
echo &#39;<br/>&#39;;
//添加新元素的新数组
print_r($a);
echo &#39;<br/>&#39;;
$a1=array("a"=>"red","b"=>"green",12=>"54",15=>"65456");
print_r(array_unshift($a1,"blue"));
echo &#39;<br/>&#39;;
print_r($a1);
?>

Output results:

In the above example, elements are added through the array_unshift function. If there are elements with numeric key names in the array, the key names will be reassigned from 0 after the function is run.

Let’s take a look at how to add elements to the end of the array.

<strong><span style="font-size: 20px;">array_push</span></strong>Function - Add elements to the end of the array

In PHP, you can delete the element at the end of the array and add an element to the end of the array. The array_push function can add an element to the end of the array. The basic syntax format of the array_push function is as follows :

array_push(array,value1,value2...)

What needs to be noted is:

The parameter array represents the array to which elements need to be added, and the parameter value12 identifies is waiting for the elements to be added to the array array. The result returned by the function successfully is the number of elements in the new array.

Let’s look at the use of the array_push function through an example. The example is as follows:

<?php
$a=array("a"=>"red","b"=>"green");
//返回结果的值
print_r(array_push($a,"blue"));
echo &#39;<br/>&#39;;
//添加新元素的新数组
print_r($a);
?>

Output result:

In the above example, the array_push function can be used to add an element to the end of the array.

In the previous article, when adding an element at the beginning of the array through the array_unshift function, if the key name in the array is a number, the key name of the element in the array will be reassigned. Below we Let’s take an example to see what impact the numeric key names of the elements in the array will have on the output results when running the array_push function to add the last element to the function. The example is as follows:

<?php
$a=array("a"=>"red","b"=>"green");
//返回结果的值
print_r(array_push($a,"blue"));
echo &#39;<br/>&#39;;
//添加新元素的新数组
print_r($a);
echo &#39;<br/>&#39;;
$a1=array("a"=>"red","b"=>"green",12=>"54",15=>"65456");
print_r(array_push($a1,"blue"));
echo &#39;<br/>&#39;;
print_r($a1);
?>

Output result:

It can be found in the above example that when adding elements at the end of the array through the array_push function, the array will not be Elements with numeric keys are reassigned keys.

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