Summary of php array function array_key_exists
The
array_key_exists() function determines whether the specified key exists in an array. If the key exists, it returns true, otherwise it returns false
array_key_exists(key, array);
key: required. Specifies key name
array: required. Specifies the input array
<?php
$a = array('a'=>'Dog','b'=>'Cat');
if(array_key_exists('a',$a)){
echo 'Key exists!';
} else{
echo 'Key does not exist!';
}
?>
Output: Key exists!
Why is array_key_exists faster than in_array?
array_key_exists and in_array query different things, right?
array_key_exists determines whether there is a key value
array_key_exists(a,arr)->if(isset(arr[a])) is true
And in_array needs to traverse the value traversal Break out of the loop when it arrives
Question:
Is the index of the array a separate storage unit, and it has been optimized? The time complexity of array_key_exists is o(1), while in_array is o(n) ??
Follow up :
This is the case in terms of complexity
array_key_exists is to determine whether a certain key has a value
in_array. If you want to traverse once to get whether they are the same, you don’t know if you have to traverse it in case of construction
The difference between isset and array_key_exists in PHP
1 .The judgment of the array value is different. For the value is null or '' or false, isset returns false, array_key_exists returns true;
2. The execution efficiency is different, isset is a built-in operator, array_key_exists is a PHP built-in function, isset is faster Some. Please refer to: PHP function implementation principle and performance analysis
3. When using isset to access a non-existentindexarray value, it will not cause a PHP error message of E_NOTICE;
4.array_key_exists will call get_defined_vars to determine whether the array variable is Exists, isset is not used;
Test code:
<?php
function
microtime_float()
{
list($usec, $sec) = explode(" ", microtime());
return ((float)$usec + (float)$sec);
}
$test_arr['aa']='dd';
$test_arr['bb']='';
$test_arr['cc']=NULL;
$test_arr['dd']=false;
$test_arr= array('aa'=>'dd','bb'=>'','cc'=>null,'dd'=>false);
echo "isset aa is ";var_dump(isset($test_arr['aa']));echo "n";
echo "isset bb is ";var_dump(isset($test_arr['bb']));echo "n";
echo "isset cc is ";var_dump(isset($test_arr['cc']));echo "n";
echo "isset dd is ";var_dump(isset($test_arr['cc']));echo "n";
echo "isset none is ";var_dump(isset($test_arr['none']));echo "n";
echo "key_exist aa is ";var_dump(array_key_exists('aa',$test_arr));echo "n";
echo "key_exist bb is ";var_dump(array_key_exists('bb',$test_arr));echo "n";
echo "key_exist cc is ";var_dump(array_key_exists('cc',$test_arr));echo "n";
echo "key_exist dd is ";var_dump(array_key_exists('dd',$test_arr));echo "n";
echo "key_exist none is ";var_dump(array_key_exists('none',$test_arr));echo "n";
$time_start = microtime_float();
for($i=0;$i<100;$i++){
isset($test_arr['aa']);
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo "isset 100 is $timen";
for($i=0;$i<10000;$i++){
isset($test_arr['aa']);
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo "isset 10000 is $timen";
for($i=0;$i<1000000;$i++){
isset($test_arr['aa']);
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo "isset 1000000 is $timen";
//++++++++++++++++++++++++++++++
$time_start = microtime_float();
for($i=0;$i<100;$i++){
array_key_exists('aa',$test_arr);
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo "array_key_exists 100 is $timen";
for($i=0;$i<10000;$i++){
array_key_exists('aa',$test_arr);
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo "array_key_exists 10000 is $timen";
for($i=0;$i<1000000;$i++){
array_key_exists('aa',$test_arr);
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo "array_key_exists 1000000 is $timen";
The above is a summary of the PHP array function array_key_exists, including indexing. I hope it will be helpful to friends who are interested in PHP tutorials.
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
What does the identity attribute in SQL mean?
Feb 19, 2024 am 11:24 AM
What is Identity in SQL? Specific code examples are needed. In SQL, Identity is a special data type used to generate auto-incrementing numbers. It is often used to uniquely identify each row of data in a table. The Identity column is often used in conjunction with the primary key column to ensure that each record has a unique identifier. This article will detail how to use Identity and some practical code examples. The basic way to use Identity is to use Identit when creating a table.
How SpringBoot monitors redis Key change events
May 26, 2023 pm 01:55 PM
1. Function Overview Keyspace notification allows clients to receive events that modify Rediskey changes in some way by subscribing to channels or patterns. All commands that modify key keys. All keys that received the LPUSHkeyvalue[value…] command. All expired keys in the db database. Events are distributed through Redis's subscription and publishing functions (pub/sub), so all clients that support subscription and publishing functions can directly use the keyspace notification function without any modifications. Because the current subscription and publishing functions of Redis adopt a fireandforget strategy, if your program
How to solve the problem of batch deletion of key values in redis
May 31, 2023 am 08:59 AM
Problems encountered: During the development process, you will encounter keys that need to be deleted in batches according to certain rules, such as login_logID (ID is a variable). Now you need to delete data such as "login_log*", but redis itself only has batch query. Command keys for class key values, but there is no command for batch deletion of a certain class. Solution: Query first, then delete, use xargs to pass parameters (xargs can convert pipe or standard input (stdin) data into command line parameters), execute the query statement first, and then remove the queried key value and the original del parameters. delete. redis-cliKEYSkey* (search condition)|xargsr
Unpatchable Yubico two-factor authentication key vulnerability breaks the security of most Yubikey 5, Security Key, and YubiHSM 2FA devices
Sep 04, 2024 pm 06:32 PM
An unpatchable Yubico two-factor authentication key vulnerability has broken the security of most Yubikey 5, Security Key, and YubiHSM 2FA devices. The Feitian A22 JavaCard and other devices using Infineon SLB96xx series TPMs are also vulnerable.All
Five selected Go language open source projects to take you to explore the technology world
Jan 30, 2024 am 09:08 AM
In today's era of rapid technological development, programming languages are springing up like mushrooms after a rain. One of the languages that has attracted much attention is the Go language, which is loved by many developers for its simplicity, efficiency, concurrency safety and other features. The Go language is known for its strong ecosystem with many excellent open source projects. This article will introduce five selected Go language open source projects and lead readers to explore the world of Go language open source projects. KubernetesKubernetes is an open source container orchestration engine for automated
PHP determines whether a specified key exists in an array
Mar 21, 2024 pm 09:21 PM
This article will explain in detail how PHP determines whether a specified key exists in an array. The editor thinks it is very practical, so I share it with you as a reference. I hope you can gain something after reading this article. PHP determines whether a specified key exists in an array: In PHP, there are many ways to determine whether a specified key exists in an array: 1. Use the isset() function: isset($array["key"]) This function returns a Boolean value, true if the specified key exists, false otherwise. 2. Use array_key_exists() function: array_key_exists("key",$arr
Sort array using Array.Sort function in C#
Nov 18, 2023 am 10:37 AM
Title: Example of using the Array.Sort function to sort an array in C# Text: In C#, array is a commonly used data structure, and it is often necessary to sort the array. C# provides the Array class, which has the Sort method to conveniently sort arrays. This article will demonstrate how to use the Array.Sort function in C# to sort an array and provide specific code examples. First, we need to understand the basic usage of the Array.Sort function. Array.So
Go language development essentials: 5 popular framework recommendations
Mar 24, 2024 pm 01:15 PM
"Go Language Development Essentials: 5 Popular Framework Recommendations" As a fast and efficient programming language, Go language is favored by more and more developers. In order to improve development efficiency and optimize code structure, many developers choose to use frameworks to quickly build applications. In the world of Go language, there are many excellent frameworks to choose from. This article will introduce 5 popular Go language frameworks and provide specific code examples to help readers better understand and use these frameworks. 1.GinGin is a lightweight web framework with fast
