Compress & Extract Linux commands

tar -zcvf archive.tar.gz directory/    => compressing folder
tar -zxvf archive.tar.gz                   => extracting the compressed file

PNG to Jpeg in PHP using GD library

<?php
function png2jpg($originalFile, $outputFile, $quality) {
    $image = imagecreatefrompng($originalFile);
    imagejpeg($image, $outputFile, $quality);
    imagedestroy($image);
}
png2jpg("img/test.png", "img/".time().".jpg", 100);
if ($handle = opendir('img/')) {
	$i=0;
   while (false !== ($entry = readdir($handle))) {
      if ($entry != "." && $entry != "..") {
         echo "<img src='img/$entry' width=150 height=100>    ";
			if($i%10==0 && $i!=0){
				echo "<br>";
			}
			$i++;
      }
   }
   closedir($handle);
}
?>

Multple checkbox selected or not

<script type="text/javascript" src='jquery.js'></script>
<script type="text/javascript">
$(document).ready(function() {
$('#extend_auto_expired').click(function(){
$("input[type=checkbox]:checked").each(function() {
alert( $(this).val() );
});
});
});
</script>
<center>
<form name='ck'>
<?php
for($r=0; $r<10;$r++){
echo "<input type='checkbox' name='t[]' value='$r'>$r<br>";
}
?>
<input type="button" id="extend_auto_expired" value="Extend auto expired" class="buttongreen" name="Submit">
</form>
<center>