Searching and highlighting one or more words in a text - Example with string/text predefined

highlightText.php

<?php

function highlightText(string $str, array $keyw = [], bool $accurate = false)
{
    if (empty($keyw)) return false;

    $sText = implode('|', $keyw);

    $match = ($accurate) ? '@\b(' . $sText . ')\b@si' : '@(' . $sText . ')@si';

    return preg_replace(
        $match,
        '<strong style="background-color:yellow">$1</strong>',
        $str
    );
}

function searchText(string $mystring, string $word)
{
    $offset = $pos = 0;
    $arrPos = [];

    do {
        $pos = stripos($mystring, $word, $offset);

        if (is_integer($pos)) {
            $arrPos[] = $pos;
            $offset = ($pos + strlen($word));
        }
    } while(is_integer($pos));

    if (!empty($arrPos)) return $arrPos;

    return false;
}

if (isset($_POST['keyws']) && !empty($_POST['keyws'])) {
    $mystring = "This will be the text that will be highlighted with our little function in PHP.";

    $dw = htmlentities($_POST['keyws']);
    $dw = trim($dw);

    if (!empty($dw)) {
        $words = explode(" ", $dw);
        $ccn = count($words);
        
        $notfound = 0;

        foreach($words as $word) {
            $findIt = searchText($mystring, $word);
            if (!$findIt) ++$notfound;
        }
        
        echo (empty($notfound) OR $notfound < $ccn) 
            ? highlightText($mystring, $words, true) 
            : "No matches found with the words indicated.";
    }
}

echo "
<form name='frmSearch' method='POST' action='" . $_SERVER['PHP_SELF'] . "'>
    <input type='text' name='keyws' value='' />
    <input type='submit' value='Search' />
</form>";