How to check if an element exists in an array in php

Two methods to check whether there are elements in the array: 1. Use "===" to determine whether the array is "[]", the syntax is "array ===[]", if TRUE is returned, there is no element in the array There are elements, otherwise there are elements in the array; 2. Use count() or sizeof() to calculate the length of the array and determine whether the length of the array is 0. The syntax is "count(array)==0". If it is 0, there is no element in the array. There are elements, otherwise there are elements in the array.

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

php checks whether the array is Methods for existing elements

Check whether there are elements in the array, which is to check whether the array is an empty array (if it is an empty array, there are no elements in the array).

Method 1: Use "===" to determine whether the array is "[]"

• If TRUE is returned, it is an empty array. Then there is no element in the array
  

• If FALSE is returned, it is not an empty array, then there is an element in the array
  

<?php  
header("content-type:text/html;charset=utf-8");
function f($arr){
	// 检查数组是否为空
	if($arr===[]) 
	    echo "数组中不存在元素"; 
	else
	    echo "数组中存在元素"; 
}


$array = array();
var_dump($array);
f($array);

$array = array(1,2,3);
var_dump($array);
f($array);
?>

Method 2: Use count() or sizeof() function

An array with a length of 0 is called an "empty array". An empty array is a real object that only contains 0 elements.

Therefore, we can use the count() function to calculate the length of the array, and then determine whether the length is 0; if it is 0, it is an empty array, otherwise it is not an empty array.

count($arr,$m)

$m: is an optional parameter and can be omitted.

• If the $m parameter is omitted, or set to COUNT_NORMAL or 0, the count() function will not detect multidimensional arrays;

• If If $m is set to COUNT_RECURSIVE or 1, the count() function will recursively calculate the number of elements in the array, which is especially useful for calculating the number of elements in multi-dimensional arrays.

Example:

<?php  
header("content-type:text/html;charset=utf-8");
function f($arr){
	// 检查数组是否为空
	if(count($arr)) 
	    echo "数组中存在元素"; 
	else
	    echo "数组中不存在元素"; 
}


$array = array();
var_dump($array);
f($array);

$array = array(1,2,3);
var_dump($array);
f($array);
?>

## The sizeof() function is an alias of the count() function, that is The function and usage of the sizeof() function are exactly the same as the count() function.

<?php  
header("content-type:text/html;charset=utf-8");
function f($arr){
	// 检查数组是否为空
	if(sizeof($arr)) 
	    echo "数组中存在元素"; 
	else
	    echo "数组中不存在元素"; 
}

$array = array();
var_dump($array);
f($array);
?>

Extended knowledge: Check whether the specified element exists in the array

Method 1: Use the in_array() function

In PHP, if you want to query whether a certain value exists in an array, you can directly use the built-in function in_array()

in_array() function to search the array Whether the specified value exists in . Returns TRUE if the value is found in the array, FALSE otherwise.

Example:

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$sites = array("Google", "phpcn", "Taobao", "Facebook");
if (in_array("phpcn", $sites)){
    echo "存在指定值";
}
else{
    echo "不存在指定值";
}
?>

Method 2: Use array_search() function

array_search() The function searches for a key value in the array and returns the corresponding key name.

You can also use this function to query whether a certain value exists in the array. If it exists, the corresponding key name will be returned. If it does not exist, it will return false.

Example:

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$sites = array("Google", "phpcn", "Taobao", "Facebook");
if (array_search("red", $sites)){
    echo "存在指定值";
}
else{
    echo "不存在指定值";
}
?>

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