How to check if letter is upper or lower in PHP?

Question

I have texts in UTF-8 with diacritic characters also, and would like to check if first letter of this text is upper case or lower case. How to do this?

Answer 1

It is my opinion that making a preg_ call is the most direct, concise, and reliable call versus the other posted solutions here.

echo preg_match('~^\p{Lu}~u', $string) ? 'upper' : 'lower';

My pattern breakdown:

~      # starting pattern delimiter 
^      #match from the start of the input string
\p{Lu} #match exactly one uppercase letter (unicode safe)
~      #ending pattern delimiter 
u      #enable unicode matching

Please take notice when ctype_ and < 'a' fail with this battery of tests.

Code: (Demo)

$tests = ['âa', 'Bbbbb', 'Éé', 'iou', 'Δδ'];

foreach ($tests as $test) {
    echo "\n{$test}:";
    echo "\n\tPREG:  " , preg_match('~^\p{Lu}~u', $test)      ? 'upper' : 'lower';
    echo "\n\tCTYPE: " , ctype_upper(mb_substr($test, 0, 1))  ? 'upper' : 'lower';
    echo "\n\t< a:   " , mb_substr($test, 0, 1) < 'a'         ? 'upper' : 'lower';

    $chr = mb_substr ($test, 0, 1, "UTF-8");
    echo "\n\tMB:    " , mb_strtoupper($chr, "UTF-8") == $chr ? 'upper' : 'lower';
}

Output:

âa:
    PREG:  lower
    CTYPE: lower
    < a:   lower
    MB:    lower
Bbbbb:
    PREG:  upper
    CTYPE: upper
    < a:   upper
    MB:    upper
Éé:               <-- trouble
    PREG:  upper
    CTYPE: lower  <-- uh oh
    < a:   lower  <-- uh oh
    MB:    upper
iou:
    PREG:  lower
    CTYPE: lower
    < a:   lower
    MB:    lower
Δδ:               <-- extended beyond question scope
    PREG:  upper  <-- still holding up
    CTYPE: lower
    < a:   lower
    MB:    upper  <-- still holding up

If anyone needs to differentiate between uppercase letters, lowercase letters, and non-letters see this post.

---

It may be extending the scope of this question too far, but if your input characters are especially squirrelly (they might not exist in a category that Lu can handle), you may want to check if the first character has case variants:

\p{L&} or \p{Cased_Letter}: a letter that exists in lowercase and uppercase variants (combination of Ll, Lu and Lt).

• Source: https://www.regular-expressions.info/unicode.html

To include Roman Numerals ("Number Letters") with SMALL variants, you can add that extra range to the pattern if necessary.

https://www.fileformat.info/info/unicode/category/Nl/list.htm

Code: (Demo)

echo preg_match('~^[\p{Lu}\x{2160}-\x{216F}]~u', $test) ? 'upper' : 'not upper';

Answer 2

As used in Kohana 2 autoloader function:

echo $char < 'a' ? 'uppercase' : 'lowercase';

When a string character is cast to integer it evaluates to its ASCII number. As you know in the ASCII table first there are some control characters and others. Then the uppercase letters from the Latin alphabet. And then the lowercase letters from the Latin alphabet. Thus you can easily check whether the code of a letter is smaller or bigger than the small latin character a.

BTW this is around twice as fast than a solution with regular expressions.

Answer 3

Another possible solution in PHP 7 is using IntlChar

IntlChar provides access to a number of utility methods that can be used to access information about Unicode characters.

$tests = ['âa', 'Bbbbb', 'Éé', 'iou', 'Δδ'];

foreach ($tests as $test) {
    echo "{$test}:\t";
    echo IntlChar::isUUppercase(mb_substr($test, 0, 1)) ? 'upper' : 'lower';
    echo PHP_EOL; 
}

Output:

âa:     lower
Bbbbb:  upper
Éé:     upper
iou:    lower
Δδ:     upper

While @mickmackusa's solution is good, it will give wrong result for different general category values (other than "Lu" uppercase letter category )

For example

• Ⅷ => ⅷ
• Ⅼ => ⅼ
• Ⅿ => ⅿ
• Ⅾ => ⅾ
• Ⅽ => ⅽ

---

 var_dump(preg_match('~^\p{Lu}~u', 'Ⅷ') ? 'upper' : 'lower'); // Resutl: lower
 var_dump(preg_match('~^\p{Lu}~u', 'ⅷ') ? 'upper' : 'lower'); // Result: lower

But

var_dump(IntlChar::isUUppercase(mb_substr('Ⅷ', 0, 1)) ? 'upper' : 'lower'); // Result: upper    
var_dump(IntlChar::isUUppercase(mb_substr('ⅷ', 0, 1)) ? 'upper' : 'lower'); // Result: lower   

Make sure to use IntlChar::isUUppercase but not IntlChar::isupper if you want to check for characters that are also uppercase but have a different general category value

Note: This library depends on intl (Internationalization extension)

Answer 4

if(ctype_upper(&value)){
    echo 'uppercase';
}
else {
    echo 'not upper case';
}

Answer 5

Note that PHP provides the ctype family like ctype_upper.

You have to set the locale correctly via setLocale() first to get it to work with UTF-8.
See the comment on ctype_alpha for instance.

Usage:

if ( ctype_upper( $str[0] )) {
    // deal with 1st char of $str is uppercase
}

Answer 6

What about just:

if (ucfirst($string) == $string) {dosomething();}