<?php
$checkbox = "false"; // Checkbox selected in form. Use literal string for value of checkbox.

$keywords = "fix, beacon";// Search terms entered into form. Use combination of known whole words and partial matches for testing.
$keywords = str_replace(" ","",$keywords);// Close all empty spaces to meet syntax requirements.
$keywords = explode(",",$keywords); // If there are multiple keywords, convert them into an array, otherwise is_array appears to return single words as 'false'.

if($checkbox == "true") // If "whole words only" is checked
    {
    if(is_array($keywords))
        {
        $search = "'[[:<:]]".implode("[[:>:]]|[[:<:]]",$keywords)."[[:>:]]'"; // Whole word REGEXP search for multiple keywords.
        }
    else
        {
        $search = "'[[:<:]]".$keywords."[[:>:]]'"; // Whole word REGEXP search for single keywords.
        }
    }
else
    {
    if(is_array($keywords))
        {
        $search = "'".implode("|",$keywords)."'"; // Any word REGEXP search for multiple keywords.
        }
    else
        {
        $search = "'".$keywords."'"; // Any word REGEXP search for single keywords.
        }
    }
echo $search; // Error checking

$sql = ("SELECT column FROM table WHERE column REGEXP $search");
if(!$result_sql = $mysqli->query($sql))
    {
    echo "It broke"; // Change this to something more appropriate.
    }

while($result = $result_sql->fetch_assoc())
    {
    $column = $result['column'];
    if($checkbox == "true") // If "whole words only" is checked
        {
        if(is_array($keywords))
            {
            foreach($keywords as $word)
                {
                $pattern = "/b".$word."b/i"; // Adds 'b' before and after the word for whole words only.
                $column = preg_replace($pattern,"<span class="highlight">".$word."</span>", $column); // Applies the highlight CSS to each word found.
                }
            }
        else
            {
            $pattern = "/b".$word."b/i"; // // Adds 'b' before and after the word for whole words only.
            $column = preg_replace($pattern,"<span class="highlight">".$word."</span>", $column); // Applies the highlight CSS to each word found.
            }
        }
    else
        {
        if(is_array($keywords))
            {
            foreach($keywords as $word)
                {
                $pattern = "/".$word."/i";
                $column = preg_replace($pattern,"<span class="highlight">".$word."</span>", $column); // Applies the highlight CSS to each word found.
                }
            }
        else
            {
            $pattern = "/".$word."/i";
            $column = preg_replace($pattern,"<span class="highlight">".$word."</span>", $column); // Applies the highlight CSS to each word found.
            }
        }
    echo "column: ".$column;
    }
?>