[GNDI]

Originally Posted by navjotjsingh

But I don't have access to php.ini file...I am on a shared hosting.

you can add

php_value memory_limit 24M

to you .httaccess file, this will SOMETIMES overright the default settings.
You can change the value of 24M to whatever you like.

If the .htaccess method does not work or if you get an internal server error after adding this line, remove the line from the .htaccess again. You can also try to change the memory_limit by adding the following line right after '<?php ' in global.php

ini_set("memory_limit","32M");