ctype_lower

(PHP 4 >= 4.0.4, PHP 5, PHP 7)

Check for lowercase character(s)

bool ctype_lower ( string $text )

Checks if all of the characters in the provided string, text, are lowercase letters.

Parameters:

text

The tested string.

Returns:

Returns TRUE if every character in text is a lowercase letter in the current locale.

Notes:

If an integer 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.

Examples:

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.