正则表达式在php中将String大写字母转换为小写

Question

Here is my problem

In a single PHP file, demonstrate a regular expression to convert "123 Tree Street, Connecticut" into "123_tree_street_connecticut" .

I have successfully replace spaces and comma with _ , but unable to change character case using Regular expression in php.

what i have did is

<?php
echo preg_replace('/(,\s|\s)/', '_', '123 Tree Street, Connecticut');
?> 

It replaces spaces and commas with _ but not able to change it's case.

Can any one guide me to how it is done Using php and regular expression only.

Thanks.

Answer 1

Since the regex replacement will use the strtolower() function, I see no reason to not just do it all with simple string functions:

<?php

$str = '123 Tree Street, Connecticut';
$str = strtolower(str_replace(array(', ', ' '), '_', $str));

print_r($str);

?>

If strtolower() is not "allowed", you could perform a shift based on the character table distance between upper- and lowercase letters. It's not pretty but it seems to work (in this specific case):

<?php

function shiftToLower($char) {
    $ord = ord($char);
    return $ord < 65 || $ord > 90 ? '_' : chr($ord + 32); // 65 = A, 90 = Z
}

$str = '123 Tree Street, Connecticut';
$str = preg_replace('/([, ]+|[A-Z])/e', "shiftToLower('\\1')", $str);

print_r($str);

?>

Answer 2

请改用strtolower功能。

Answer 3

Input :

<?php
// either use this //
echo str_replace(',', '', str_replace(' ', '_', strtolower("123 Tree Street, Connecticut")));

echo "\n";

// or use this //
echo str_replace(array(', ', ' '), '_', strtolower("123 Tree Street, Connecticut"));
?>

Output :

123_tree_street_connecticut
123_tree_street_connecticut

Hope this helps you. Thanks!!

Answer 4

I am not sure there is any built-in regex solution for to change the case. But I think you can do it by hands by writing a new regex for every character.

Converting to upper case example:

$new_string = preg_replace(
    array('a', 'b', 'c', 'd', ....),
    array('A', 'B', 'C', 'D', ....),
    $string
);

I think you got the point.