ugarit

<html>
  <head><title>Test</title></head>
<body>
  
<?php
 
$string1="a    b    c d/e-f";
$string2=preg_replace( '/\s+/', '\s', $string1);
$string3=preg_replace( "/\\\s/", "s+", preg_quote( $string2, '/' ) );
 
echo "string1=[$string1]<br>";
echo "string2=[$string2]<br>";
echo "preg_quote($string2)=".preg_quote($string2)."<br>";
echo "string3=[$string3]<br>";
      
?>
 
</form>
</body>
</html>