How to determine whether there is a value in an array in php

PHP is one of the most popular open source server-side languages ​​in the world. It provides a wealth of array operation functions that can easily perform various operations on arrays. In actual development, we often need to determine whether a value exists in an array. This article will introduce several methods to determine whether there is a value in an array in PHP.

1. Use the in_array() function

The in_array() function is a function provided by PHP to determine whether a value exists in an array. Its usage is very simple, you only need to pass in two parameters, the first parameter is the value to be searched, and the second parameter is the array to be searched. The in_array() function returns a Boolean value indicating whether the value being searched exists in the array.

The following is a sample code that uses the in_array() function to determine whether a value exists in an array:

<?php
$numbers = array(1, 2, 3, 4, 5);
if (in_array(3, $numbers)) {
    echo "3 存在于数组中";
} else {
    echo "3 不存在于数组中";
}
?>

The output result is:

3 存在于数组中

It should be noted that in_array( ) function distinguishes data types when determining whether a value exists in an array. In other words, if you want to determine whether a string exists in an array, you must use a string type value as the first parameter.

2. Use the array_search() function

array_search() function can also be used to determine whether a value exists in an array. Its usage is similar to the in_array() function, and it also needs to pass in two parameters. The first parameter represents the value to be searched, and the second parameter represents the array to be searched. The array_search() function returns the subscript (index) of the element if it finds an element equal to the value it is looking for, or false if it is not found.

The following is a sample code that uses the array_search() function to determine whether a value exists in an array:

<?php
$numbers = array(1, 2, 3, 4, 5);
$key = array_search(3, $numbers);
if ($key !== false) {
    echo "3 所在的下标为 " . $key;
} else {
    echo "3 不存在于数组中";
}
?>

The output result is:

3 所在的下标为 2

It should be noted that array_search( ) function also distinguishes data types when determining whether a value exists in an array.

3. Use the array_key_exists() function

array_key_exists() function can be used to determine whether a specified key exists in the array. Its first parameter represents the key to be searched, and the second parameter represents the array to be searched. The array_key_exists() function returns true if the specified key is found, false otherwise.

The following is a sample code that uses the array_key_exists() function to determine whether a value exists in an array:

<?php
$numbers = array("one" => 1, "two" => 2, "three" => 3, "four" => 4, "five" => 5);
if (array_key_exists("three", $numbers)) {
    echo "数字 3 存在于数组中";
} else {
    echo "数字 3 不存在于数组中";
}
?>

The output result is:

数字 3 存在于数组中

It should be noted that array_key_exists( ) function can only be used to find the keys of an array, not the values ​​of the array.

To sum up, you can use the in_array() function, array_search() function and array_key_exists() function to determine whether a value exists in the array. When choosing which function to use, you need to decide based on actual needs. If you need to determine whether a value exists in an array, you can use the in_array() function or array_search() function. If you need to determine whether a specified key exists in an array, you can use the array_key_exists() function. No matter which function is used, pay attention to the distinction between data types to avoid incorrect results.

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