Uppercase

In PHP programs we sometimes need to convert the cases of letters in strings. For example, we may have a lowercase string and require an Uppercase string.

It would be possible to iterate over the characters in a string and convert them. But it is much easier to use a built-in function like strtoupper.

Example

This program introduces several strings and then converts them with built-in functions. It prints the resulting strings.

Part 1 We invoke strtoupper. This takes all lowercase characters and changes them to uppercase.

Part 2 With strtolower, we convert characters that are already uppercase, and change them to lowercase.

Part 3 For these functions (like strtoupper), digits, punctuation and whitespace are left alone.

// Part 1: convert a string to uppercase.
$value = "bird";
$upper = strtoupper($value);
var_dump($upper);

// Part 2: convert a string to lowercase.
$value = "CAT";
$lower = strtolower($value);
var_dump($lower);

// Part 3: non-letters are not affected.
$value = "123 z?";
$upper = strtoupper($value);
var_dump($upper);
string(4) "BIRD"
string(3) "cat"
string(6) "123 Z?"

First letters

There are some helpful functions in the PHP standard library that only convert the first letter in strings. And we can even target each word in a single call.

Part 1 We call ucfirst to uppercase the first letter in a string. If the first character is not a letter, the function has no effect.

Part 2 We lowercase the first letter. All the remaining letters are left unchanged.

Part 3 With ucwords, we uppercase each letter that is either the first letter in the string, or follows a space character.

Part 4 Ucwords will not handle uppercasing the letter after a hyphen or other non-space character.

// Part 1: uppercase first letter.
$value = "test";
$result = ucfirst($value);
var_dump($result);

// Part 2: lowercase first letter.
$value = "TEST";
$result = lcfirst($value);
var_dump($result);

// Part 3: uppercase all words.
$value = "one two three";
$result = ucwords($value);
var_dump($result);

// Part 4: words begin after a space only.
$value = "one-two, hello";
$result = ucwords($value);
var_dump($result);
string(4) "Test"
string(4) "tEST"
string(13) "One Two Three"
string(14) "One-two, Hello"

Sometimes in programs we need to normalize the casing of strings—for example, all data should be lowercase. Functions like strtolower are ideal for this purpose.