How to Make First Letter Uppercase and the Rest Lowercase in a PHP String?

To make the first letter of a PHP string uppercase and the rest lowercase, you can do the following:

1. Make string lowercase (using strtolower());
2. Capitalize only the first letter (using ucfirst()).

This would return a new string with first letter capitalized and all remaining characters in lowercase (regardless of the case in the original string). For example:

$str = "FOO BAR";
$capStr = ucfirst(strtolower($str));

echo $capStr; // "Foo bar"

This, of course, does not consider any grammar-specific capitalization rules (such as capitalizing the first letter at the start of each new sentence or after certain punctuations, etc.):

$str = "fOO BAR BAZ. Qux Qaz Quux.";
$capStr = ucfirst(strtolower($str));

echo $capStr; // "Foo bar baz. qux qaz quux."

As you can see in the example above, there are two sentences in the string, but only the first letter of the entire string is capitalized and all remaining words are converted to lowercase.