PHP function to check if a string is all lowercase [closed] - php

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I'm trying to create a function that returns TRUE if a string is all lowercase without using any built-in PHP functions. How can I do that?
This is what I was working with, but using ctype_lower.
$string = "string";
if (ctype_lower($string)) {
echo $string . ' is all lowercase letters.';
} else {
echo $string . ' is not all lowercase letters.';
}

Answer 1

Well, if you just want a simple-purpose check, you could just compare the original string with an strtolowerred string. Of course, it won't be foolproof. Like this:
function check_lowercase_string($string) {
return ($string === strtolower($string));
}
$string = 'Hi! I am a string';
var_dump(check_lowercase_string($string)); // false
var_dump(check_lowercase_string('test')); // true
A painful attempt of no functions:
function check_lowercase_string($string) {
$chars = '';
// map all small characters
for($alpha = 'a'; $alpha != 'aa'; $alpha++) { $small[] = $alpha; }
$l = 0; // not strlen() :p
while (#$string[$l] != '') {
$l++;
}
for($i = 0; $i < $l; $i++) { // for each string input piece
foreach($small as $letter) { // for each mapped letter
if($string[$i] == $letter) {
$chars .= $letter; // simple filter
}
}
}
// if they are still equal in the end then true, if they are not, false
return ($chars === $string);
}
var_dump(check_lowercase_string('teSt')); // false

Answer 2

You can either use ctype_lower, which is inbuilt, so you don't want that :c.
But you can use the answer from here. And put together a loop which checks for the first character. If uppercase then return true, and if not, then remove the first character of string and continue like that through the entire string.