How to validate that a string only contain lowercase letters?

Question

I\'m trying to verify that my string matches a pattern. That is, the full string can be written as that pattern. However preg_match returns true, i

Answer 1

I super-love regex, but not for this task -- it is needless overhead because there is a single, direct, non-regex equivalent. https://www.php.net/manual/en/function.ctype-lower.php

Code: (Demo)

$tests = [
    'Test',
    'test',
    'test1',
    '1test',
    'test!'
];
foreach ($tests as $test) {
    echo "$test: " , (ctype_lower($test) ? 'true' : 'false') , "\n";
}

Output:

Test: false
test: true
test1: false
1test: false
test!: false

p.s. For the record, an empty string returns false. I'm not sure of your logical validation requirements for this test unit.