Case Conversion in PHP: Uppercase and Lowercase

Case conversion in PHP refers to changing the letters of a string from uppercase to lowercase or vice versa. PHP offers several built-in functions that make this process straightforward. They are:

• strtolower() Function
• strtoupper() Function
• ucfirst() Function
• ucwords() Function

Lowercase Conversion with PHP strtolower() Function

PHP provides a built-in function named strtolower() that is used to convert all alphabetic characters in a string to lowercase. You can use the strtolower() function in the following cases:

• To make comparisons case-insensitive.
• To store consistent data (like emails, usernames).
• For formatting URLs or SEO slugs.
• When accepting user input in various cases.

The general syntax to define strtolower() function in PHP is as follows:

strtolower(string $string): string

This function accepts an input string $string as argument that you want to convert to lowercase.

Return Value

The strtolower() function returns the lowercase version of the input string. So, you have to store it using a variable.

Example 1:

<?php
$text = "SCIENTECH EASY";

// Converting characters of a string from uppercase to lowercase.
$lowercaseText = strtolower($text);
echo $lowercaseText;
?>

Output:
       scientech easy

<?php
$input = "Admin";
$storedUsername = "admin";

if (strtolower($input) === strtolower($storedUsername)) {
     echo "User authenticated.";
} else {
     echo "Invalid username.";
}
?>

Output:
       User authenticated.

Upper Case Conversion using PHP strtoupper() Function

The strtoupper() function in PHP is a built-in function that is used to convert all alphabetic characters of a string into uppercase. The general syntax to define strtoupper() function is as follows:

strtoupper(string $string): string

In the above syntax, the parameter $string represents the input string that you want to convert to uppercase.

Return Value

The strtoupper() function returns the uppercase version of the input string.

Example 3:

<?php
$text = "Scientech Easy";

// Converting the characters of string from mixed to uppercase.
$uppercaseText = strtoupper($text);
echo $uppercaseText;
?>

Output:
       SCIENTECH EASY

Capitalizing the First Letter using ucfirst() Function

The ucfirst() function in PHP is a built-in function that is used to capitalize the first character of a string. The general syntax to define the ucfirst() function is as follows:

ucfirst(string $string): string

Example 4:

<?php
$text = "hello world!";

// Capitalizing the first letter of a string using ucfirst() function.
$capitalized = ucfirst($text);
echo $capitalized;
?>

Output:
      Hello world!

Capitalizing the First Letter of Each Word using ucwords() Function

The ucwords() function is a built-in function provided by PHP that is used to capitalize the first letter of each word in a string. The basic form of this function is as:

ucwords(string $string): string

Example 5:

<?php
$text = "introduction to php programming!";

// Capitalizing the first letter of each word.
$capitalizedWords = ucwords($text);
echo $capitalizedWords;
?>

Output:
      Introduction To Php Programming!

In this tutorial, we have learned about case conversion in PHP with the help of various examples. I hope that you will have understood that how to convert characters of a string into upper or lower case. Here’s a quick recap of PHP’s case conversion functions:

• strtolower(): Converts all characters to lowercase.
• strtoupper(): Converts all characters to uppercase.
• ucfirst(): Capitalizes the first character of a string.
• ucwords(): Capitalizes the first character of each word.