How to check if letter is upper or lower in PHP?
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?
Solution 1:
function starts_with_upper($str) {
$chr = mb_substr ($str, 0, 1, "UTF-8");
return mb_strtolower($chr, "UTF-8") != $chr;
}
Note that mb_substr is necessary to correctly isolate the first character.
Working Demo Online
Solution 2:
Use ctype_upper
for check upper case:
$a = array("Word", "word", "wOrd");
foreach($a as $w)
{
if(ctype_upper($w{0}))
{
print $w;
}
}
Solution 3:
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';
Solution 4:
Tried ?
$str = 'the text to test';
if($str{0} === strtoupper($str{0})) {
echo 'yepp, its uppercase';
}
else{
echo 'nope, its not upper case';
}