PHP 8.1 array_is_list()

PHP 8 introduced a new function called array_is_list(). This function is a valuable addition for developers working with arrays. It helps in determining whether a given array is a list or not. Understanding how to use array_is_list() can streamline array operations, especially in scenarios where the structure of the array impacts its processing or behavior.

Understanding List-like Arrays in PHP

The array_is_list() function in PHP 8 checks if a given array is a list. An array is considered a list when its keys are consecutive integers starting from 0, with no gaps in between. For instance, [0 => 'HTML', 1 => 'JavaScript', 2 => 'PHP'] is a list, but [1 => 'HTML', 0 => 'JavaScript', 2 => 'PHP'] is not, as it does not start with 0.

Why is array_is_list() Important?

Before PHP 8, developers had to write custom code to verify whether an array was a list. This process was not only time-consuming but also prone to errors. With the introduction of array_is_list(), it is now simpler to determine the nature of an array, which is especially useful in functions that expect list-type arrays.

Syntax of array_is_list()

The syntax of the array_is_list() function is as follows:

bool array_is_list ( array $array )

This function takes an array as its argument and returns a boolean value: true if the array is a list and false otherwise.

Examples of Using array_is_list()

Let's see some examples of how to use the array_is_list() function in PHP.

Checking a Simple Array

Here, you'll see how the function is applied to different arrays to check if they are lists:

<?php
$array1 = [0 => 'HTML', 1 => 'JavaScript', 2 => 'PHP'];
$array2 = [1 => 'HTML', 0 => 'JavaScript', 2 => 'PHP'];
$array3 = ['HTML', 'JavaScript', 'PHP'];

echo var_dump(array_is_list($array1)); // Returns true
echo var_dump(array_is_list($array2)); // Returns false
echo var_dump(array_is_list($array3)); // Returns true
?>

In the above example, $array1 and $array3 are considered lists because their keys are consecutive integers starting from 0. $array2 is not a list, as its keys are not in the correct order.

Checking an Associative Array

In this example, we have an associative array of fruits to check if it is a list format:

<?php
// Define an associative array of fruits
$fruits = ['apple' => 'red', 'banana' => 'yellow', 'orange' => 'orange'];

// Check if the array is a list
var_dump(array_is_list($fruits)); // bool(false)
?>

The output is false because the array has string keys, not integers.

Checking an Array With Gaps

Consider an array with gaps in its keys:

<?php
// Define an array of colors with gaps
$colors = [0 => 'red', 2 => 'green', 5 => 'blue'];

// Check if the array is a list
var_dump(array_is_list($colors)); // bool(false)
?>

The output is false due to the non-sequential keys.

Real-World Application

Imagine you are processing students' attendance reports and need to ensure that the data is in a list format:

<?php
function generateAttendanceReport(array $attendanceList)
{
    // Validate that the attendance list is formatted as a sequential list
    if (!array_is_list($attendanceList)) {
        return "Error: Attendance data must be a sequential list.";
    }

    $presentCount = 0;
    // Process each attendance record
    foreach ($attendanceList as $attendance) {
        if ($attendance['status'] === "Present") {
            $presentCount++;
        }
    }

    $totalStudents = count($attendanceList);
    $attendancePercentage =
        $totalStudents > 0 ? ($presentCount / $totalStudents) * 100 : 0;

    return "Attendance: " .
        round($attendancePercentage, 2) .
        "% (Present: $presentCount, Total: $totalStudents)";
}

// Example of a properly formatted list of attendance records
$attendanceList = [
    ["name" => "Student1", "status" => "Present"],
    ["name" => "Student2", "status" => "Absent"],
    ["name" => "Student3", "status" => "Present"],
    ["name" => "Student4", "status" => "Absent"],
    ["name" => "Student5", "status" => "Present"],
    // ... more records
];

// Process and output the attendance report
echo generateAttendanceReport($attendanceList);
?>

The above example demonstrates array_is_list() in action, ensuring data integrity.

Conclusion

This tutorial guided you through using PHP 8's array_is_list() function. You learned about its purpose, syntax, and practical applications. Incorporating this function into your PHP projects can significantly enhance your efficiency in array handling and ensure greater data integrity, mainly when working with JSON data or user inputs.