Increase file size upload limit using php.ini or htaccess

Increasing file upload size by php.ini

File upload size affected by mainly below PHP settings.
file_uploads = On
This setting must be on. It allows running uploads through HTTP.
Ensure this value is on the value can be On/Off or 1/0 or true/false.
upload_max_filesize = 20M
This value limits the size of uploaded single file. Give it value what ever your requirements.
post_max_size = 40M
This value limits the size of all the uploaded content. For example upload_max_filesize is for single file, if we upload 3 files simultaneously each 15mb total 45mb so it exceeds post_max_size.
Remember post_max_size must be larger about 40% of upload_max_filesize.

max_execution_time = 30
Generally image uploading and manipulating with GD or Imagemagic consumes much time. So it may exceeds 30 seconds. You can modify whatever your requirements. When a script execution time exceeded by this limit the server stops the scripts or gives fatal error.

memory_limit = 128M
Generally image uploading and manipulation with GD or Imagemagic consumes much server memory. When it exceeds this memory the server stops executing the script, then we see empty page or no response from server or we get a fatal error.

Completed example, to increase 10Mb
upload_max_filesize = 10M ;
post_max_size = 20M ;
memory_limit = 128M

Copy the above settings into your php.ini and put it in your web root directory.
Increasing file upload size by .htaccess

php_value upload_max_filesize 10M
php_value post_max_size 20M
php_value memory_limit 128M

Copy the above settings into your .htaccess file and put it in your web root directory.
Almost all web host providers give to override the .htacces ,so you can use above method.