How to check if an array has a key-value pair in php

Implementation steps: 1. Define an array containing only specified key-value pairs, with the syntax "$variable name=["key name"=>"key value"];"; 2. Use array_intersect_assoc() The function compares the key-value pair array with the original array. The syntax "array_intersect_assoc (original array, key-value pair array)" will return an intersection array containing the same elements. 3. Determine whether the intersection array is an empty array. The syntax "intersect Array ===[]", if it is empty, there is no key-value pair specified in the array.

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

In PHP, you can use the array_intersect_assoc() function To check whether the array has the specified key-value pair.

Implementation steps:

Step 1: Define an array containing only specified key-value pairs

$变量名=["键名"=>"键值"];

Step 2: Use the array_intersect_assoc() function to compare the key-value array with the original array

The array_intersect_assoc() function is used to compare two (or more) arrays The key name and key value, and returns the intersection (an intersection array containing the same elements).

array_intersect_assoc(原数组,键值对数组)

Step 3: Determine whether the intersection array is an empty array

交集数组===[]

• If it is empty, there is no specified key-value pair in the array

• If it is not empty, there is a specified key-value pair in the array

Implementation code:

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);
function f($arr,$s){
	$assoc=array_intersect_assoc($arr,$s);
	// 检查数组是否为空
	if($assoc===[]) {
		echo "数组中没有指定键值对"; //数组为空
	}
	    
	else{
		echo "数组中有指定键值对"; //数组不为空
	}  
}

$arr=array("a"=>"red","b"=>"green","c"=>"blue","d"=>"yellow");
echo &#39;原数组：&#39;;
var_dump($arr);
$s=["b"=>"green"];
echo &#39;指定键值对：&#39;;
var_dump($s);

f($arr,$s);
?>

Description:

array_intersect_assoc() function--compare the key name and key value of the array

This function compares two (or more) array keys and values, and returns an intersection array that includes the sum of all keys in the compared array (array1) and any other parameter arrays (array2 or array3, etc.) key value.

array_intersect_assoc(array1,array2,array3...)

Parameters	Description
array1	Required . The first array to compare with other arrays.
array2	Required. The array to compare to the first array.
array3,...	Optional. Additional array to compare with the first array.

Return value: Returns an intersection array, which includes all the arrays being compared (array1), as well as any other parameter arrays (array2 or array3, etc. etc.) in the key name and key value.

Extended knowledge: Two other methods to determine empty arrays

Method 1: 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.

<?php  
header("content-type:text/html;charset=utf-8");
// 声明一个空数组
$empty_array = array(); 
   
// 检查数组是否为空
if(count($empty_array) == 0) 
    echo "数组为空"; 
else
    echo "数组不为空"; 
?>

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

Method 2: Use the empty() function

The empty() function is used to check whether a variable is empty.

empty() Determines whether a variable is considered empty. When a variable does not exist, or its value is equal to FALSE, then it is considered not to exist. empty() does not generate a warning if the variable does not exist.

Note: Any uninitialized variable, a variable with a value of 0 or false or an empty string "" or null, an empty array, or an object without any attributes will be judged as empty==true

Returns FALSE when the variable exists and is a non-empty and non-zero value, otherwise returns TRUE.

<?php  
header("content-type:text/html;charset=utf-8");
// 声明一个空数组
$array = []; 
   
// 检查数组是否为空
if(empty($array)) 
    echo "数组为空"; 
else
    echo "数组不为空"; 
?>

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