There are several ways to define arrays in php

There are 5 ways to define arrays in php, namely: 1. Use array to create an array; 2. Use "$arr[] = 'a';" to create an array; 3. Use "array(1= >'jack',2=>'lucy',500=>'hcoder')" to create an array; 4. Use "$arr[1] = 'jack';" to create an array; 5. Use " Create an array using $arr['name'] = '';".

The operating environment of this tutorial: Windows 10 system, PHP version 8.1, DELL G3 computer

How many ways to define an array in PHP?

5 ways to create arrays in PHP

In PHP and other programming language programming, the creation of arrays is often used in front-end development. , JS array creation can be directly created and assigned by [] and new Array(). But what are the ways to create arrays in PHP? After reviewing the information and collecting and sorting it online, I summarized it:

##1. Using array to create an array is the most common and convenient way:

$arr = array('a','b','c');
$arr[] = 'a' ; $arr[] = 'b' ; $arr[] = 'c';
$arr = array('name' => '关羽' , 'age' => 23 , 'sex' => '男')；

2 . Sometimes you need to create a random array with a length of len, so you can use range():

Definition: array range(first, second, step) //first: element Minimum value second: maximum value of element step: element step size (amount to be increased)

$number = range(0,5);
print_r ($number);
  
//打印：Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 [4] => 4 [5] => 5 )
  
$number = range(0,50,10);
print_r ($number);
  
//打印：Array ( [0] => 0 [1] => 10 [2] => 20 [3] => 30 [4] => 40 [5] => 50 )
  
$letter = range("a","d");
print_r ($letter);
  
//打印：Array ( [0] => a [1] => b [2] => c [3] => d )

　3. Of course, under certain specific requirements, certain variables need to be stored in arrays, and the variable names of these variables Convert to key name, variable value to key value (premise: the variable exists):

$firstname = "Peter";
$lastname = "Griffin";
$age = "38";
$result = compact("firstname", "lastname", "age");
print_r($result);
  
//打印： Array ( [firstname] => Peter [lastname] => Griffin [age] => 38 )
  
$firstname = "Peter";
$lastname = "Griffin";
$age = "38";
$name = array("firstname", "lastname");
$result = compact($name, "location", "age");
print_r($result);
  
//打印：Array ( [firstname] => Peter [lastname] => Griffin [age] => 38 )
//由于$location变量不存在，所以存入不了数组

4. Merge the two arrays into a new array, the value of the first array is the key of the new array name, the value in the second array is the key value of the new array:

Definition: The array_combine() function can combine two arrays into a new array, one of which is The key name, the value of another array is the key value.

$a1=array("a","b","c","d");
$a2=array("Cat","Dog","Horse","Cow");
print_r(array_combine($a1,$a2));
  
//打印：Array ( [a] => Cat [b] => Dog [c] => Horse [d] => Cow )

5. Create an array with a fixed length like the key value:

Definition: array_fill(start,number,value) //start: starting index number: Number of values ​​value: array value

$a=array_fill(2,3,"Dog");
print_r($a);
  
//打印：Array ( [2] => Dog [3] => Dog [4] => Dog )

Create array format:

First format

$Array name = array('value' , 'value', 'value',...);

This format does not specify the key of the element in the array. PHP will automatically create the key in the form of a number, starting from 0 and accumulating in sequence.

Format of calling array: $array name[numeric key]

<?php 
$arr = array(&#39;a&#39;,&#39;b&#39;,&#39;c&#39;); echo $arr[1]; //输出

Second format

$array name[] = 'value ';

$array name[] = 'value';

$array name[] = 'value';

......

This kind The format also does not specify the keys of the elements in the array. PHP will automatically create the keys in the form of numbers, starting from 0 and accumulating sequentially.

Format of calling array: $array name[numeric key];

<?php 
$arr[] = &#39;a&#39;; $arr[] = &#39;b&#39;; $arr[] = &#39;c&#39;; echo $arr[1]; //输出b

The third format

$数组名称 = array(数字类型的键=> ‘值’, 数字类型的键 => ‘值’, 数字类型的键=> ‘值’,……);

Calling format: $array name [key of numeric type];

<?php 
$arr = array(1=>&#39;jack&#39;,2=>&#39;lucy&#39;,500=>&#39;hcoder&#39;); echo $arr[500]; //输出hcoder

This format uses integers as the keys of the array. PHP’s support for arrays is very flexible and you can define the numbers in the array arbitrarily.

If there are duplicate keys in the array, the last element will overwrite all previous keys, and the last one will be a valid value.

The 4th format

$Array name[integer type key] = 'value';

$Array name [Integer type key] = 'value';

$Array name[Integer type key] = 'Value';

......

Calling format: $Array name[ Integer type key];

<?php 
$arr[1] = &#39;jack&#39;; $arr[2] = &#39;lucy&#39;; $arr[500] = &#39;hcoder&#39;; echo $arr[500]; //输出hcoder

The 5th format (associative array)

$数组名称=array(‘字符串形式的键’=>’值’,‘字符串形式的键’=>’值’,……);

Calling format: $array name['key in string form'];

<?php 
$arr = array(&#39;name&#39;=>&#39;张三&#39;, &#39;age&#39;=>18); echo $arr[&#39;age&#39;]; //输出18

The 6th format (associative array)

$Array name['Key in string form']=>'Value';

$Array Name['Key in string form']=>'Value';
......

Calling format: $array name['Key in string form'];

<?php 
$arr[&#39;name&#39;] = &#39;张三&#39;; $arr[&#39;age&#39;] = 18; echo $arr[&#39;age&#39;]; //输出18

In short, use $a[] and $a=array()

Recommended learning: "

PHP Video Tutorial"

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