在PHP中找到字符串时更改类

I have:

$keyword = 'blue';

I want to insert a special class when in a string the system found blue.

For example:

This sky is <span class="blue">blue</a>.

This pear is green.

I have actually:

$string = "The sky is blue."; 
if (stripos($string, $keyword) !== false) {
    // The string is found, now change the class
}

Thanks a lot.

Is this what you are looking for?

$keyword = 'blue';
$replace = 'green';
$string = "The sky is blue."; 
if (stripos($string, $keyword) !== false) {
   $string = str_ireplace(array($keyword), $replace , $string);
}

You could use regexps, as in:

function format_keywords($html, $keywords) {
    foreach ($keywords as $keyword) {
        $keyword = preg_quote($keyword);
        $html = preg_replace("/\b$keyword\b/i", "<span class=\"$keyword\">$keyword</span>", $html);
    }
    return $html;
}

For example, this:

format_keywords("This sky is blue.", array("is", "blue"));

Would yield:

This sky <span class="is">is</span> <span class="blue">blue</span>?

Note that This has not been recognized, thanks to the \b delimiters.

See the documentation: