An example of str_replace with user selected values from HTML dropdowns

PHP Code
Output
<!doctype html>
<html>

<head>

<style>
.divcls {
  background: #004000;
  height: auto;
  width:290px;
  border-radius: 15px;
  padding:20px;
  font-size:17px;
  color:#fff;   
}
span{
    background: #FFFF00;
    color:#000;
    font-size:20px;
    
}
.srcstring{
    background: #800040;
  height: auto;
  width:290px;
  border-radius: 15px;
  padding:20px;
  font-size:17px;
  color:#fff;      
}
.replaced_string{
    background: #804000;
  height: auto;
  width:290px;
  border-radius: 15px;
  padding:20px;
  font-size:17px;
  color:#fff;       
}
.btncls{
    background-color:#FC2209;
    border: #2e6da4;
  	font-family: Arial, Geneva, Arial, Helvetica,  sans-serif;
	font-size: 15px;
    color: #FFFFFF;
    letter-spacing: 1px;
    padding: 8px 12px;
    font-size: 14px;
    font-weight: normal;

    border-radius: 4px;
    line-height: 1.5;
    text-decoration:none;
} 
</style>
 

  
</head>
<body>
<form method="post" target="">
<div class="divcls"><p>A demo with user selected terms</p>
<p><label>Replace Term: </label><select name="searchstr">
    <option value="targetted">targetted</option>
    <option value="search term">search term</option>
    <option value="function">function</option>
</select>
</p>
<p>
<label>To be Replaced with: </label><select name="replacestr">
    <option value="destinated">destinated</option>
    <option value="needle">needle</option>
    <option value="method">method</option>
</select>
</p>

<p><input type="submit" class="btncls" value="Execute str_replace function"></p>

</div>  
<p class="srcstring"><strong>The source string<br /><br /></strong>
The str_replace method is used to perform replacement in targetted string by the given search term.<br> The str_replace is case-sensitive function.
</p>

</div>
</form>
< ?php
$search_string=$_POST["searchstr"];
$replace_string=$_POST["replacestr"];
$source_string = ("The str_replace method is used to perform replacement in targetted string by the given search term.<br> The str_replace is case-sensitive function.");

if ($search_string != ""){
    $str_replaced = str_ireplace($search_string, "<span>" .$replace_string ."</span>", $source_string);
    
   // echo "The source string: <BR>" .$source_string ."<BR><BR><BR>";
    echo "<p class='replaced_string'><strong>The replaced string: <br /><br /></strong>" .$str_replaced . "</p>";
}
?>

</div>
</body>
</html>