PHP Program to Check Vowel or Consonant

Use PHP to check if a character is a vowel by testing if it is in ['a','e','i','o','u'] (case-insensitive), else it is a consonant; for example, if (in_array(strtolower($char), ['a','e','i','o','u'])) { echo 'Vowel'; } else { echo 'Consonant'; }.

Examples

Inputa

OutputVowel

InputB

OutputConsonant

Inputz

OutputConsonant

How to Think About It

To check if a character is a vowel or consonant, first convert it to lowercase to handle uppercase letters. Then compare it against the list of vowels a, e, i, o, u. If it matches any vowel, print 'Vowel'; otherwise, print 'Consonant'.

Algorithm

1

Get the input character from the user.

2

Convert the character to lowercase.

3

Check if the character is in the list of vowels (a, e, i, o, u).

4

If yes, print 'Vowel'.

5

Otherwise, print 'Consonant'.

Code

php

<?php
$char = 'A';
$charLower = strtolower($char);
$vowels = ['a', 'e', 'i', 'o', 'u'];
if (in_array($charLower, $vowels)) {
    echo "Vowel";
} else {
    echo "Consonant";
}
?>

Output

Vowel

Dry Run

Let's trace the input 'A' through the code

1

Input character

$char = 'A'

2

Convert to lowercase

$charLower = 'a'

3

Check if vowel

'a' is in ['a','e','i','o','u'] → true

4

Print result

Output: Vowel

Step	Variable	Value
1	$char	'A'
2	$charLower	'a'
3	in_array check	true
4	Output	Vowel

Why This Works

Step 1: Convert to lowercase

Using strtolower() ensures the check works for both uppercase and lowercase letters.

Step 2: Check vowel membership

The in_array() function checks if the character is one of the vowels in the array.

Step 3: Output result

If the character is a vowel, print 'Vowel'; otherwise, print 'Consonant'.

Alternative Approaches

Using switch statement

php

<?php
$char = 'e';
switch (strtolower($char)) {
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
        echo "Vowel";
        break;
    default:
        echo "Consonant";
}
?>

Switch is clear and readable but less flexible if vowels list changes.

Using regular expression

php

<?php
$char = 'I';
if (preg_match('/[aeiou]/i', $char)) {
    echo "Vowel";
} else {
    echo "Consonant";
}
?>

Regex is concise and handles case-insensitivity but may be less intuitive for beginners.

Complexity: O(1) time, O(1) space

Time Complexity

Checking membership in a small fixed array of vowels is constant time, O(1), since the array size does not grow.

Space Complexity

Only a small fixed array of vowels is stored, so space complexity is O(1).

Which Approach is Fastest?

Using in_array() or a switch statement both run in constant time and are efficient; regex is slightly slower but more flexible.

Approach	Time	Space	Best For
in_array with array	O(1)	O(1)	Simple and clear checks
switch statement	O(1)	O(1)	Readable fixed cases
regular expression	O(1)	O(1)	Flexible pattern matching