PHP Math Exercises: Create a human-readable random string for a captcha

Last update on June 02 2025 13:00:27 (UTC/GMT +8 hours)

11. Human-Readable Captcha String

Write a PHP function to create a human-readable random string for a captcha.

Sample Solution:

PHP Code:

<?php
// Define a function named random_string with a default length of 5
function random_string($length = 5)
{ 
    // Define a string of characters without vowels and 'x'
    $chars = 'bcdfghjklmnpqrstvwxyz';

    // Initialize an empty string to store the result
    $result = '';

    // Iterate through the specified length to generate random characters
    for ($x = 0; $x < $length; $x++)
    {
        // Alternate between consonants and vowels while generating characters
        $result .= ($x % 2) ? $chars[mt_rand(13, 21)] : $chars[mt_rand(0, 12)];
    }

    // Return the generated random string
    return $result;
}

// Call the random_string function and echo the result
echo random_string();
?>

Output:

rasyn

Explanation:

In the exercise above,

function random_string($length = 5): This line defines a function named "random_string()" with one parameter '$length', which has a default value of 5 if not provided.
$chars = 'bcdfghjklmnpqrstvwxyz';: This line defines a string of characters containing consonants excluding 'x'. Vowels and 'x' are omitted to avoid inappropriate strings.
$result = '';: This line initializes an empty string to store the generated random string.
for ($x = 0; $x < $length; $x++): This line starts a loop that iterates from 0 to the specified length, generating random characters.
$result .= ($x % 2) ? $chars[mt_rand(13, 21)] : $chars[mt_rand(0, 12)];: This line generates random characters alternately from consonants and vowels. It uses the modulus operator to determine whether the index of the character to be chosen is even or odd.
return $result;: This line returns the generated random string.
echo random_string();: This line calls the "random_string()" function without providing a length, so it uses the default length of 5, and echoes the generated random string.

Flowchart :

$Flowchart: Create a human-readable random string for a captcha$

For more Practice: Solve these Related Problems:

Write a PHP function to generate a captcha string that alternates between consonants and vowels to enhance readability.
Write a PHP script to create a random, pronounceable string for captcha purposes by using phonetic patterns.
Write a PHP program to produce a captcha string that includes both letters and numbers, ensuring a balanced mix.
Write a PHP function to generate a human-readable captcha by shuffling predetermined syllable fragments and concatenating them.

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PHP Code Editor:

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