PHP determines whether it is an array

In PHP, we often deal with arrays, and when dealing with arrays, we need to determine whether a given variable is an array type. This is a very basic operation. In this article, we will learn how to determine if an array is an array in PHP.

1. What is an array?

In computer science, an array is a data structure used to store data of the same type. Arrays can store multiple elements, and each element can be accessed through an index. In PHP, arrays can store different types of data, including integers, floating point numbers, strings, objects, etc.

2. How to determine whether it is an array?

In PHP, we can use the is_array() function to determine whether a given variable is an array type.

Syntax:

boolean is_array (mixed $var)

Parameters:

$var: Variables that need to be judged

Return value :

If $var is an array type, return TRUE; otherwise, return FALSE.

Sample code:

$arr1 = array(1, 2, 3, 4, 5); // 正确的数组
$arr2 = "hello world"; // 不是数组
$arr3 = 123; // 不是数组
$arr4 = array('name' => 'Tom', 'age' => 20); // 正确的数组

var_dump(is_array($arr1)); // true
var_dump(is_array($arr2)); // false
var_dump(is_array($arr3)); // false
var_dump(is_array($arr4)); // true

?>

In the above example, we defined four variables $arr1, $arr2, $arr3 and $arr4. $arr1 and $arr4 are array types, $arr2 and $arr3 are not array types. We used the var_dump() function to print the return values ​​of these four variables through the is_array() function.

3. Determine multi-dimensional arrays

In addition to one-dimensional arrays, PHP also supports multi-dimensional arrays. In PHP, a multidimensional array is an array that contains one or more arrays as elements. So, how to judge multi-dimensional arrays?

We can use the array_filter() function and count() function to judge multi-dimensional arrays. The array_filter() function is used to filter the array, and the count() function is used to count the number of elements in the array.

Sample code:

$arr1 = array(1, 2, 3, 4, 5); // 一维数组
$arr2 = array( array(1, 2), array(3, 4), array(5, 6) ); // 二维数组

// 判断一维数组
if ( is_array($arr1) && count($arr1) > 0 && array_filter($arr1, 'is_array') == false ) {
    echo "arr1是一维数组";
} else {
    echo "arr1不是一维数组";
}

// 判断二维数组
if ( is_array($arr2) && count($arr2) > 0 && array_filter($arr2, 'is_array') ) {
    echo "arr2是二维数组";
} else {
    echo "arr2不是二维数组";
}

?>

In the above sample code, we define two arrays, $ arr1 is a one-dimensional array, $arr2 is a two-dimensional array. We use the is_array() function to determine the array type, the count() function to calculate the number of array elements, and the array_filter() function to filter the array. Because the two-dimensional array contains one or more sub-arrays, we need to use the array_filter() function to filter the array. Return false to indicate that it is a two-dimensional array, and return true to indicate that it is not a two-dimensional array.

4. Summary

This article introduces how to determine whether it is an array in PHP. One-dimensional arrays can be judged using the is_array() function, while multi-dimensional arrays need to be judged using the array_filter() function and count() function. When dealing with arrays, it is very important to determine whether it is an array, which can prevent some errors in the program.

The above is the detailed content of PHP determines whether it is an array. For more information, please follow other related articles on the PHP Chinese website!