(PHP 4 >= 4.0.4, PHP 5, PHP 7)
ctype_lower — Check for lowercase character(s)
ctype_lower ( mixed $text ) : bool
Checks if all of the characters in the provided string, text, are lowercase letters.
text
The tested string.
Note:
If an int between -128 and 255 inclusive is provided, it is interpreted as the ASCII value of a single character (negative values have 256 added in order to allow characters in the Extended ASCII range). Any other integer is interpreted as a string containing the decimal digits of the integer.
Returns true if every character in text is a lowercase letter in the current locale.
Example #1 A ctype_lower() example (using the default locale)
<?php
$strings = array('aac123', 'qiutoas', 'QASsdks');
foreach ($strings as $testcase) {
if (ctype_lower($testcase)) {
echo "The string $testcase consists of all lowercase letters.\n";
} else {
echo "The string $testcase does not consist of all lowercase letters.\n";
}
}
?> The above example will output:
The string aac123 does not consist of all lowercase letters. The string qiutoas consists of all lowercase letters. The string QASsdks does not consist of all lowercase letters.
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https://www.php.net/manual/en/function.ctype-lower.php