How to find array subscript in php

Two methods: 1. Use array_keys, the syntax "array_keys(array, search value, false|true)" will return an array containing subscripts. 2. Traverse the array and store the subscript into an empty array with the syntax "foreach(array as $k=>$v){$r[]=$k;}".

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, DELL G3 computer

Array array is a set of ordered variables. Each value is called an element. Each element is distinguished by a special identifier called a key (also called a subscript).

So how to find the array subscript in PHP? Two methods are introduced below.

Method 1: Directly use the built-in function array_keys()

array_key() function can get some or all key names (subscripts) in the array, the function syntax The format is as follows:

array_keys($array,$search_value,$strict)

Parameter description is as follows:

• $array: required parameter, which is the array to be operated;
• $search_value: Optional parameter. If the parameter is empty, the function will return all the key names in the array. If this parameter is specified, the function will only return the key name with the value $search_value;
• $strict: Optional parameter to determine whether to use strict mode when searching. $strict defaults to false, which is non-strict mode. Only types are compared during search, not types. If $strict is set to true, that is Strict mode, compares both value and type when searching, equivalent to ===.

array_key() function will return the obtained array key name in the form of an array.

Example 1: All key names

<?php
$arr=array("Peter"=>65,"Harry"=>80,"John"=>78,"Clark"=>90);
var_dump($arr);
var_dump(array_keys($arr));
?>

Example 2: Key names of specified values

<?php
$arr=array("Peter"=>65,"Harry"=>80,"John"=>78,"Clark"=>90);
var_dump($arr);
var_dump(array_keys($arr,80));
var_dump(array_keys($arr,"80"));
var_dump(array_keys($arr,"80",true));
?>

Method 2: Use the foreach statement to traverse the array and store the key name into an empty array

<?php
$arr=array("Peter"=>65,"Harry"=>80,"John"=>78,"Clark"=>90);
var_dump($arr);
$r=[];
foreach($arr as $k=>$v){
	$r[]=$k;
}
var_dump($r);
?>

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