How to determine whether an array is an index array in php

Judgment steps: 1. Use array_keys() to get all the key names of the original array, the syntax is "array_keys(array)"; 2. Use array_filter() to filter the array, the syntax is "function f($v){return (is_string($v));}$res=array_filter($keys,"f");" will return a filter array containing string elements; 3. Determine whether the filter array is an empty array, and if it is empty, the array is an index array.

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

In php, the subscript of the index array ( Key name) consists of numbers. If a key name in an array is not a number, then the array is an associative array (not an index array).

So you only need to determine whether the key names of the array are all numbers to determine whether an array is an index array.

Implementation steps:

Step 1: Use the array_keys() function to obtain all the key names of the original array

array_keys( ) function returns a new array containing all the keys in the array.

array_keys(array,value,strict)

Parameters	Description
array	Required . Specifies an array.
value	Optional. You can specify a key value, and then only the key name corresponding to that key value will be returned.
strict	Optional. Used with the value parameter. Possible values: true - Returns the key name with the specified key value. Depending on the type, the number 5 is not the same as the string "5". false - the default value. Independent of type, the number 5 is the same as the string "5".

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$arr=array("r"=>"red",2,3,"hello",5,6);
var_dump($arr);
$keys=array_keys($arr);
var_dump($keys);
?>

Step 2: Use array_filter() and is_string() functions to filter the array and return The string elements in the key name array

function f($v){
	 return(is_string($v));
}
$res=array_filter($keys,"f");
var_dump($res);

will return a filtered array containing string elements

Step 3: Judgment Filter whether the array is an empty array

$res==[]

• If it is empty, the array is an index array

• If it is not empty, the array It is not an index array, it is an associative array

Implementation code:

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
function f($v){
		 return(is_string($v));
}
function fun($arr){
	$keys=array_keys($arr);
	
	$res=array_filter($keys,"f");
	if($res==[]){
		echo "数组是索引数组<br>";
	}else{
		echo "数组不是索引数组，是关联数组<br>";
	}
}


$arr=array("r"=>"red",2,3,"hello",5,6);
var_dump($arr);
fun($arr);
$arr=array(1,2,3,"hello",5,6);
var_dump($arr);
fun($arr);
?>

Recommended study: "PHP video tutorial》

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