How can text from a text file be replaced with an image (smiley) in PHP?

To replace text from a text file with an image (smiley) in PHP, you can read the contents of the text file, use a regular expression to find the text you want to replace, and then output the text with the image instead. You can use the `preg_replace()` function to replace the text with the image HTML code.

<?php
// Read the contents of the text file
$text = file_get_contents('textfile.txt');

// Replace the text with an image (smiley)
$text_with_smiley = preg_replace('/\b(smiley)\b/', '<img src="smiley.png" alt="smiley">', $text);

// Output the text with the image
echo $text_with_smiley;
?>