[php] Html encode in PHP

What is the easiest way to Html encode in PHP?

Encode.php

<h1>Encode HTML CODE</h1>

<form action='htmlencodeoutput.php' method='post'>
<textarea rows='30' cols='100'name='inputval'></textarea>
<input type='submit'>
</form>

htmlencodeoutput.php

<?php

$code=bin2hex($_POST['inputval']); 
$spilt=chunk_split($code,2,"%");
$totallen=strlen($spilt);
 $sublen=$totallen-1;
 $fianlop=substr($spilt,'0', $sublen);
$output="<script>
document.write(unescape('%$fianlop'));
</script>";

?> 
<textarea rows='20' cols='100'><?php echo $output?> </textarea> 

You can encode HTML like this .

Try this:

<?php
    $str = "This is some <b>bold</b> text.";
    echo htmlspecialchars($str);
?>

I searched for hours, and I tried almost everything suggested.
This worked for almost every entity :

$input = "ažškunrukiš ? àéò ??? ©€ ?? ? ?? ? R?";


echo htmlentities($input, ENT_HTML5  , 'UTF-8');

result :

āžšķūņrūķīš ○ àéò ∀∂∋ ©€ ♣♦ ↠ ↔↛ ↙ ℜ℞rx;