preg_replace() with a string contains "*" character - php

Question

I have made a script to highlight a word in a string. The script is below.
function highlight_text($text, $words){
$split_words = explode( " " , $words );
foreach ($split_words as $word){
$color = '#FFFF00';
$text = preg_replace("|($word)|Ui", "<span style=\"background:".$color.";\">$1</span>", $text );
}
return $text;
}
$text = '*bc';
$words = '*';
echo highlight_text($text, $words);
When running the script, I got the following error:
Warning: preg_replace(): Compilation failed: nothing to repeat at offset 1
Can anyone help me?

Answer 1

This can help you:
<?php
function highlight_text($text, $words){
$split_words = explode( " " , $words );
foreach ($split_words as $key=>$word){
if (preg_match('/[\'^£$%&*()}{##~?><>,|=_+¬-]/', $word))// looking for special characters
{
$word = preg_quote($word, '/');// if found output \ before that
}
$color = '#FFFF00';
$text = preg_replace("|($word)|Ui", "<span style=\"background:".$color.";\">$1</span>", $text );
}
return $text;
}
$text = '*bc';
$words = '*';
echo highlight_text($text, $words);

Answer 2

change "*" to "\*" and profit.

Answer 3

You can check if special character in function highlight_text
like:
function highlight_text($text, $words){
$split_words = explode( " " , $words );
foreach ($split_words as $word){
$str = '';
$word = str_split($word);
foreach ($word as $c) {
if ($c == '*') {
$str .= '\*';
}
else {
$str .= $c;
}
}
$color = '#FFFF00';
$text = preg_replace("|($str)|Ui", "<span style=\"background:".$color.";\">$1</span>", $text );
}
return $text;
}

Answer 4

Change your code to
function highlight_text($text, $words){
$split_words = explode( " " , $words );
foreach ($split_words as $word){
$color = '#FFFF00';
$word = preg_quote($word, '/');
$text = preg_replace("|$word|Ui", "<span style=\"background:".$color.";\">$0</span>", $text );
}
return $text;
}
$text = '*bc';
$words = '*';
echo highlight_text($text, $words);
then will be ok.