Word case in php

  John Mwaniki /   29 Sep 2021

As a developer, you work with strings of different nature in day-to-day projects. Some may be a word long, a phrase, a sentence, or even comprising thousands of words.

It is easy to work on and change the case on shorter strings manually, eg. you can edit the string and make a sentence begin with an uppercase letter, to change an all uppercase text to a sentence case, etc.

In the case of long strings of texts, this will not be an easy task to accomplish and may take too long. The good news is that most programming languages have a way to easily convert and manipulate the case in a string.

In this article, you will learn how to convert strings to different cases using PHP language.

Converting a string to lowercase in PHP

To change all the alphabetical characters in a string to lowercase, we use the PHP strtolower() function.

Example:

<?php
$string = "Hello World!";
echo strtolower($string);
?>

Output:

hello world!

 

Converting a string to uppercase in PHP

To change all the alphabetical characters in a string to uppercase, we use the PHP strtoupper() function.

Example:

<?php
$string = "Hello World!";
echo strtoupper($string);
?>

Output:

HELLO WORLD!

Converting the first character in a string to uppercase in PHP

To change the first alphabetical characters of a string to uppercase, we use ucfirst() function.

Example:

<?php
$string = "hello world!";
echo ucfirst($string);
?>

Output:

Hello world!

Converting the first character of each word to uppercase in PHP

To change the first character of every word in a string in PHP, we use ucwords() function.

Example:

<?php
$string = "hello world!";
echo ucwords($string);
?>

Output:

Hello World!

Converting the string to sentence case in PHP

All sentences start with an uppercase(capital) letter and end with either a full stop (.), a question mark (?), or an exclamation mark (!).

If our string comprises only one sentence, then converting it to a sentence case is very simple as we only use the ucfirst() function to convert its first character to uppercase.

Example:

<?php
$string = "which programming language do you love most?";
echo ucfirst($string);
?>

Output:

Which programming language do you love most?

However, that will not be the case with a string comprising of multiple sentences.

In such a case:

— We split the string into an array of sentences using the preg_split() function;

— We loop through all the sentences in a for each loop;

— Convert the string characters in each sentence to lower case using the strtolower() function;

— Convert the first character of every sentence to uppercase using the ucfirst() function;

— Concatenate all our sentences to form back the original string, now with a sentence case.

Example:

<?php
$string = "hello world! i am a programmer. i like programming in php.";
$sentences = preg_split('/([.?!]+)/', $string, -1, PREG_SPLIT_NO_EMPTY|PREG_SPLIT_DELIM_CAPTURE); 

$newstring = ""; 
foreach ($sentences as $sentence) { 
 $newsentence = ucfirst(strtolower(trim($sentence)));
 /*
 The above line of code trims white space at the beginning and end of the sentence.. trim()
 Converts it to lower case using strtolower()
 Then converts the first character to upper case using ucfirst()
 Then assigns it to the variable $newsentence
 */
 $newstring .= $newsentence; // Concatenate to the $newstring
 if(preg_match('/([.?!]+)/', $sentence)){
  $newstring .= " "; // Add a space after fullstop, question mark, or exclamation mark
 }
} 
echo $newstring;
?>

Output:

Hello world! I am a programmer. I like programming in php.

From the above example, you can skip the conversion to lower case if you just want all the sentences to start with an uppercase without affecting the cases of other words/characters.

Conclusion

In this article, you have learned how to convert PHP strings to upper case, lower case, the first character of every word to upper case, the first character of the string to upper case, and also how to convert a combination of multiple sentences into sentence case, where every first character of every sentence starts with an upper case.

It is my hope that the article was simple enough to follow along and easy to understand and implement.

To get notified when we add more incredible content to our site, feel free to subscribe to our free email newsletter.

The quickest way is with a bitmask. No clunky string functions or regex. PHP is a wrapper for C, so we can manipulate bits quite easily if you know your logical function like OR, NOT, AND, XOR, NAND, etc..:

function swapCase($string) {
    for ($i = 0; $i < strlen($string); $i++) {
        $char = ord($string{$i});
        if (($char > 64 && $char < 91) || ($char > 96 && $char < 123)) {
            $string{$i} = chr($char ^ 32);
        }
    }
    return $string;
}

This is what changes it:

$string{$i} = chr($char ^ 32);

We take the Nth character in $string and perform an XOR (^) telling the interpreter to take the integer value of $char and swapping the 6th bit (32) from a 1 to 0 or 0 to 1.

All ASCII characters are 32 away from their counterparts (ASCII was an ingenious design because of this. Since 32 is a power of 2 (2^5), it’s easy to shift bits. To get the ASCII value of a letter, use the built in PHP function ord():

ord('a') // 65
ord('A') // 97
// 97 - 65 = 32

So you loop through the string using strlen() as the middle part of the for loop, and it will loop exactly the number of times as your string has letters. If the character at position $i is a letter (a-z (65-90) or A-Z (97-122)), it will swap that character for the uppercase or lowercase counterpart using a bitmask.

Here’s how the bitmask works:

0100 0001 // 65 (lowercase a)
0010 0000 // 32 (bitmask of 32)
--------- // XOR means: we put a 1 if the bits are different, a 0 if they are same.
0110 0001 // 97 (uppercase A)

We can reverse it:

0110 0001 // 97 (A)
0010 0000 // Bitmask of 32
---------
0100 0001 // 65 (a)

No need for str_replace or preg_replace, we just swap bits to add or subtract 32 from the ASCII value of the character and we swap cases. The 6th bit (6th from the right) determines if the character is uppercase or lowercase. If it’s a 0, it’s lowercase and 1 if uppercase. Changing the bit from a 0 to a 1 ads 32, getting the uppercase chr() value, and changing from a 1 to a 0 subtracts 32, turning an uppercase letter lowercase.

swapCase('userId'); // USERiD
swapCase('USERiD'); // userId
swapCase('rot13'); // ROT13

We can also have a function that swaps the case on a particular character:

// $i = position in string
function swapCaseAtChar($string, $i) {
    $char = ord($string{$i});
    if (($char > 64 && $char < 91) || ($char > 96 && $char < 123)) {
        $string{$i} = chr($char ^ 32);
        return $string;
    } else {
        return $string;
    }
}

echo swapCaseAtChar('iiiiiiii', 0); // Iiiiiiii
echo swapCaseAtChar('userid', 4); // userId

// Numbers are no issue
echo swapCaseAtChar('12345qqq', 7); // 12345qqQ

Altering the case of a string is very easy with PHP’s four built-in functions:

1. strtoupper()
2. strtolower()
3. ucfirst() and
4. ucwords().

The above functions do not work on multibyte strings you should use the multibyte equivalents of those functions:

1. mb_strtolower()
2. mb_strtoupper()
3. mb_convert_case().
4. mb_ucfirst()

strtoupper

//Syntax
strtoupper(string $string): string

The strtoupper function converts string characters into upper case.

<?php
 $string = 'A Sample STRING.';
 echo strtoupper($string);
 //prints: A SAMPLE STRING.

strtolower

//Syntax
strtolower(string $string): string

The strtolower function lower cases all the characters in a string.

<?php
 $string = 'A Sample STRING.';
 echo strtolower($string);
 //prints: a sample string.

ucfirst

<?php
//Syntax
ucfirst(string $string): string

The ucfirst function capitalizes the first character of a string.

<?php
 $string = 'a Sample STRING.';
 echo ucfirst($string);
 //prints: A Sample STRING.

ucwords

<?php
//Syntax
ucwords(string $string, string $separators = " trnfv"): string

The ucwords function capitalizes the first character of every word in a string.

<?php
 $string = 'a sample string.';
 echo ucwords($string);
 //Prints: A Sample String.

The optional $separators contains the word separator characters. See the following example:

<?php
 //Single separator |
 echo ucwords ('capitalizes|the|first|character of every word', '|');
 //Capitalizes|The|First|Character of every word

 //Multiple separator | and space
 echo ucwords ('capitalizes|the|first|character of every word', '| ');
 //Capitalizes|The|First|Character Of Every Word

Change Multibyte String Case

The native string functions in PHP assume strings are an array of single bytes, so functions strtolower, strtoupper, ucwords and ucfirst will not work on multibyte strings, such as Japanese and Chinese characters. You should use the multibyte equivalents of those functions, such as mb_strtolower, mb_strtoupper and mb_convert_case.

The multi-byte functions accept another optional parameter for the character encoding. If it is omitted, the internal character encoding value will be used.

We can set the internal character encoding by using mb_internal_encoding.

<?php
  mb_internal_encoding('UTF-8');

By setting up the internal encoding, it is not necessary to provide the encoding parameter for the multibyte functions.

mb_strtolower

<?php
//Syntax:
mb_strtolower(string $string, ?string $encoding = null): string

The mb_strtolower function lower cases all the characters in a multibyte string. If the second parameter $encoding is omitted, the internal character encoding value will be used.

<?php
 $string = 'Ἇ Ђ Б';
 echo mb_strtolower($string);

 // Setting character encoding
 echo mb_strtolower($string,'UTF-8');
 //Prints: ἇ ђ б

mb_strtoupper

The mb_strtoupper function upper cases all the characters in a multi-byte string.

<?php
 $string = 'ἇ ђ б';
 echo mb_strtoupper($string);

 //Set character encoding
 echo mb_strtoupper($string,'UTF-8');
 //Prints: Ἇ Ђ Б

mb_convert_case

The mb_convert_case function convert case on the basis of the Unicode character properties, it can convert any characters that have ‘alphabetic’ property, such as A-umlaut (Ä).

<?php
 $string = 'Τάχιστη αλώπηξ βαφής ψημένη γη';
 echo mb_convert_case($string, MB_CASE_UPPER);
 //ΤΆΧΙΣΤΗ ΑΛΏΠΗΞ ΒΑΦΉΣ ΨΗΜΈΝΗ ΓΗ

 //You also can provide your desired encoding
 echo mb_convert_case($string, MB_CASE_LOWER, 'UTF-8');
 //τάχιστη αλώπηξ βαφής ψημένη γη

 echo mb_convert_case($string, MB_CASE_TITLE, 'UTF-8');
 //Τάχιστη Αλώπηξ Βαφής Ψημένη Γη

Howto capitalize the first character of a multi-byte string

PHP does not have a mb_ucfirst function but you can use the following custom function as an alternative.

mb_ucfirst function example

<?php
 function mb_ucfirst($string, $encoding = null) {
  if (empty($string))
   return $string;
  $encoding = is_null($encoding) ? mb_internal_encoding() : $encoding;
  $firstChr = mb_strtoupper(mb_substr($string, 0, 1,$encoding),$encoding);
  return $firstChr . mb_substr($string, 1, null, $encoding);
}

Creating mb_ucfirst function step by step

This step by step tutorial will elaborate the above mb_ucfirst function.

Step 1. Create function mb_ucfirst which will accept two parameters, first for the input string and the second for the character encoding. Assign NULL to encoding parameter as default values.

function mb_ucfirst($string, $encoding = null) {

}

Step 2. Check for empty string by validating it with empty function. empty function returns false if string value does not exist or equals to FALSE.

function mb_ucfirst($string, $encoding = null) {
 if (empty($string)) return;
}

Step 3. Validate second parameter $encoding with is_null function. is_null function returns true if value is null. If character encoding not provided we’ll assign internal encoding to $encoding parameter using mb_internal_encoding function.

function mb_ucfirst($string, $encoding = null) {
 if (empty($string)) return $string;
 if (is_null($encoding)) {
  $encoding = mb_internal_encoding();
 }
}

Step 4. Extract first character of the string using mb_substr function (similar to substr function but multi byte safe). mb_substr accepts four parameters : $string, $start, $length, $encoding. The $start value 0 and $lenght value 1 return the first character from the string.

function mb_ucfirst($string, $encoding = null) {
 if (empty($string)) return $string;
 if (is_null($encoding)) {
  $encoding = mb_internal_encoding();
 }
 $firstChr = mb_substr($string, 0, 1,$encoding);
}

Step 4. Change first character $firstChr case using mb_strtoupper function.

function mb_ucfirst($string, $encoding = null) {
 if (empty($string)) return $string;
 if (is_null($encoding)) {
  $encoding = mb_internal_encoding();
 }
 $firstChr = mb_substr($string, 0, 1,$encoding);
 $firstChr = mb_strtoupper($firstChr,$encoding);
}

Step 5. Now extract the remaining string (without the first character) from the original string using mb_substr function.

We’ll use 1 and null for start and length values respectively in mb_substr function, to extract all the remaining characters.

Note: If NULL is passed in length value the mb_substr function will extract all characters to the end of the string.

function mb_ucfirst($string, $encoding = null) {
 if (empty($string)) return $string;
 if (is_null($encoding)) {
  $encoding = mb_internal_encoding();
 }
 $firstChr = mb_substr($string, 0, 1,$encoding);
 $firstChr = mb_strtoupper($firstChr,$encoding);
 $remainingString = mb_substr($string, 1, null, $encoding);
}

Step 6. Now concate $firstChar and $remainingString with . and return it.

function mb_ucfirst($string, $encoding = null) {
 if (empty($string)) return $string;
 if (is_null($encoding)) {
  $encoding = mb_internal_encoding();
 }
 $firstChr = mb_substr($string, 0, 1,$encoding);
 $firstChr = mb_strtoupper($firstChr,$encoding);
 $remainingString = mb_substr($string, 1, null, $encoding);
 return $firstChr . $remainingString;
}

---

Working with Strings: