$string = " hello world! ";
$modifiedString = trim($string);  // Trim whitespace
$modifiedString = strtoupper($modifiedString);  // Convert to uppercase
$modifiedString = str_replace('WORLD', 'PHP', $modifiedString);  // Replace 'WORLD' with 'PHP'
$modifiedString = str_slug($modifiedString);  // (Example of making it URL-friendly - not built-in, just illustrative)

echo $modifiedString;  // Output: HELLO-PHP
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