How to remove all non-uppercase characters in a string?

问题

Yeah I'm basically just trying to explode a phrase like Social Inc. or David Jason to SI and DJ. I've tried using explode but couldn't figure out how to explode everything BUT the capital letters, do I need to use preg_match()?

回答1:

You can use this regex (?![A-Z]). with preg_replace() to replace every char except the one in uppercase.

preg_replace("/(?![A-Z])./", "", $yourvariable)

The regex will look for anythings NOT an uppercase letter ( ?! negative lookahead ).
I've created a regex101 if you wish to test it with other cases.

EDIT As an update of this thread, You could also use the ^ char inside the square braquets to reverse the effect.

preg_replace("/([^A-Z])./", "", $yourvariable)

This will match all char that are not uppercase and replace them with nothing.

回答2:

Quick and easy:

$ucaseletters = preg_replace('/[^A-Z]/', '', $input);

This will replace everything that is not an uppercase Letter within the Range A-Z.

Explanation:

^ within [] (Character-Set) is the negation-Operator (=anything that is NOT...)

回答3:

Nicholas and Bernhard have provided successful regex patterns but they are not as efficient as they could be.

Use /[^A-Z]+/ and an empty replacement string with preg_replace().

The negated character class has a one or more quantifier, so longer substrings are matched and fewer replacements are required.

This is the best pattern to use with preg_split as well, but preg_split generates an array, so there is the extra step of calling implode.

回答4:

I've got a more complicated solution but it works too!

$s = str_split("Social Inc.");
foreach ($s as $idx => $char) {
    if(preg_match("/[A-Z]/", $char))
    {
        echo $char;
    }
}

It will echo the upper-case letters.

回答5:

You can use preg_split php function too with regx

$pieces = preg_split('/(?=[A-Z])/',$str);

回答6:

Here is what you need to do:

$str = explode(' ', $ster);
$newStr = strtoupper($str[0][0] . $str[1][0]);

来源：https://stackoverflow.com/questions/44950173/how-to-remove-all-non-uppercase-characters-in-a-string

标签

php

regex

preg-replace

uppercase