在php preg_match_all中遇到小于（<）运算符的问题

Question

I'm trying to parse a query string and have run into something I can't quite figure out.

Trying to match a string that can contain either < or >, but I'm seeing some weird output only when the string contains a <.

Example:

<?php
$gt = 'wt>f';
preg_match_all("/([A-Za-z<>]+)/", $gt, $gtmatches);
?>

<pre><?php print_r($gtmatches); ?></pre>

Returns as expected:

Array
(
    [0] => Array
        (
            [0] => wt>f
        )

    [1] => Array
        (
            [0] => wt>f
        )
)

But simply replacing that > with a <, gives really weird output:

Code:

<?php
$lt = 'wt<f';
preg_match_all("/([A-Za-z<>]+)/", $lt, $ltmatches);
?>

<pre><?php print_r($ltmatches); ?></pre>

Outputs:

Array
(
    [0] => Array
        (
            [0] => wt Array
        (
            [0] => wt

I've tested this on PHP 5.6.24/IIS 10, and locally on PHP 5.6.32/Apache 2.4.29.

Solved thanks to iainn (damn you guys are fast!)

My browser was interpreting the < as the start of a tag, looking at the source, everything is fine.

Answer 1

You're trying to view the print_r output in a browser, and it's interpreting the < as an HTML tag, up until the end of the => a couple of lines later. If you view the page source rather than the rendered output, you'll see the results you're expecting.

As mentioned in a comment, the regex itself is working fine.