How to determine whether a key value exists in an array in php

In PHP, array is a very commonly used data type, used to store some ordered data. When we need to find whether a certain key value exists in a PHP array, we can use the in_array() function provided by PHP to determine. This article will introduce in detail how to use the in_array() function to determine whether a key value exists in a PHP array.

1. In_array() function introduction

The in_array() function is used to determine whether a value exists in the array, and the return value is true or false. It accepts two parameters, the first parameter is the value to be found, and the second parameter is the array to be found.

Function definition:

bool in_array ( mixed $needle , array $haystack [, bool $strict = FALSE ] )

Parameter description:

• needle: The value to be found.
• haystack: The array to be searched.
• strict: Optional parameter. If set to true, the equality operator is used for comparison (i.e., types and values ​​are compared), default is false (the equality operator is used for comparison, i.e., only values ​​are compared).

2. Determine whether a certain key value exists in the PHP array

In PHP, it is very simple to use the in_array() function to determine whether a certain key value exists in the array. The following is an example:

<?php 
$fruits = array("apple", "banana", "orange", "pear");
if (in_array("apple", $fruits)) {
    echo "苹果在数组中存在";
} else {
    echo "苹果在数组中不存在";
}
?>

Through the above code, we can quickly determine whether there is an element with the value "apple" in the array $fruits.

3. Determine whether a certain key exists in the PHP associative array

When we need to determine whether a certain key exists in an associative array (that is, the key corresponding to the key value in the index array), We need to use the array_key_exists() function provided by PHP. The usage of this function is similar to the in_array() function. It also receives two parameters: the first parameter is the key to be searched, and the second parameter is the array to be searched.

Function definition:

bool array_key_exists ( mixed $key , array $array )

Parameter description:

• key: the key to be searched.
• array: The array to be searched.

The following is an example:

<?php 
$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
if (array_key_exists("Peter", $age)) {
    echo "键为 Peter 的元素在数组中存在";
} else {
    echo "键为 Peter 的元素在数组中不存在";
}
?>

In the above code, we determine whether there is an element with the key "Peter" in the $age array.

Summary

Through the introduction of this article, we can see that the way to determine whether a key value exists in an array in PHP is extremely simple. We just need to use the in_array() function or array_key_exists() function. When we encounter such a requirement when writing PHP code, we can directly use these two functions to make judgments, avoiding unnecessary trouble and time costs.

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