Tech.Bitez » PHP

PHP sessions across subdomains

Wasif — Thu, 21 Aug 2008 12:04:45 +0000

If you are facing problems sharing sessions across subdomains, use the following code before session_start().

ini_set ( 'session.cookie_domain', '.mysite.com' );

Replace mysite.com with your domain name.

PHP 4 is dead, last release of PHP 4!!!

Wasif — Fri, 08 Aug 2008 17:45:21 +0000

The last release of PHP 4 is now available for download on 7th of August 2008. PHP 4 has been serving the web sites since 2000.

Should we use template engines in PHP?

Wasif — Thu, 01 May 2008 08:50:40 +0000

I came across this discussion today on pros and cons of using template engines in PHP.

Increasing file upload limit in PHP

Wasif — Fri, 14 Mar 2008 19:10:40 +0000

There are different options to increase file upload limit in PHP. First is changing PHP configuration file (php.ini) and restarting webserver or overwriting the php.ini value in .htacces (this option is available if you are running Apache).

There are 2 directives which affect upload limit i.e. upload_max_filesize and post_max_size.

Now we look at the first method. First you have to find out where the php.ini is. To find out the location, make a .php file containing only this code and place it in your webroot and point your browser to this file.

 phpinfo(); ?>

In the page output you can find Configuration File Path. Open this file and change the values for upload_max_filesize and post_max_size according to your requirement e.g. to set 10MB upload limit, the values will be
upload_max_filesize = 10M
post_max_size = 10M

After changing the values, save php.ini and restart the webserver. If you open up the above PHP file again, you'll see the updated values of upload_max_filesize and post_max_size.

In case you don't have access to php.ini (in shared hosting environment) or don't want to restart the webserver then the best option is to use .htaccess.

The syntax for .htaccess as follows
php_value upload_max_filesize 10M
php_value post_max_size 10M

Apache supports .htaccess. I am not sure if you can overwrite these settings in .htaccess with lighttpd.

Saving images in MySQL with PHP

Wasif — Wed, 18 Jul 2007 18:33:53 +0000

People have different opinions on saving images in database. Some says, "Why bother database if we can handle this by saving images to disk". I am agree with this;).

Most of the requirements can be fulfilled by saving the images to disk. This reduces the unnecessary load on MySQL.

Here is the small code to save the image in MySQL with the help of PHP.

Images are saved in MySQL as BINARY data. BINARY data can not be saved in varchar or char data types, for this purpose we need a data type which can handle binary data. BLOB columns are treated as binary strings (byte strings). The following table is fulfilling our requirements for a simple test with a BLOB field.

CREATE TABLE `images` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `image` MEDIUMBLOB NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=MyISAM;

Now we have a MySQL table ready to store the image. Next steps are easy i.e.

Read the image
Encode the image data
Save binary data in DB

These 3 steps are performed with the following PHP code

$image = chunk_split(base64_encode(file_get_contents("image.jpg")));
$query = "INSERT INTO images (image) VALUES('$image')";
mysql_query($query) or die(mysql_error());
echo "Image id is ".mysql_insert_id();

Now we have saved the image in database successfully. The next step is to display the image.

// showimage.php
header('Content-type: image/jpeg');
$query = "SELECT image from images where id=1";
$rs = mysql_fetch_array(mysql_query($query));
echo base64_decode($rs["image"]);

Ohhh!!! You wanted to display the image in HTML page. No problem, call this file as a image in .e.g.



</span></a></span>Image Test<span style="color: #009900;"><span style="color: #000000; font-weight: bold;">

 

Displaying image from database
 
 src="showimage.php" />

Download multiple files upload script

Let me know if you need some more info on this topic.

Download data as csv using PHP

Wasif — Sat, 30 Jun 2007 23:05:50 +0000

This is a very simple example to download data in csv format using PHP and MySQL. I have used a table with two columns i.e. id and name.

The main point to download file is a proper use of header(). It has said many times in many places but I repeat here, "Make sure there must not be any sort of output (including whitespaces) before header()". We can also set a default file name for the file.

Here is the PHP code


// Connect to database
mysql_connect("localhost", "root", "root");
mysql_select_db("test");
 
// mention the file name to display in download prompt
$file_name = "download.csv";
 
header("Content-type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"$file_name\"");
header("Cache-Control: cache, must-revalidate");
header("Pragma: public");
 
// Output header
echo "Id,Name"."\n";
 
$result = mysql_query("SELECT * FROM test");
while($rs = mysql_fetch_array($result))
{
	echo $rs["id"].",";
	echo $rs["name"]."\n";
}
?>

Consider the followings when downloading a large csv file

PHP script may exceed maximum execution time. To prevent this, use set_time_limit() at top of the script.
Sometimes it is beneficial to use mysql_unbuffered_query() instead of mysql_query() for huge data.

If you find any problem with this code, please inform.

Note: Do not use "ID" in the start of CSV file. Doing so will result in an error "SYLK: File format is not valid" when opening this file in Microsoft Excel.

Enable register globals

Wasif — Sat, 16 Jun 2007 13:49:23 +0000

It is strongly recommended that you do not turn on the register_globals. But if you still want to turn on register_globals then follow these steps

Make a .php file containing only this code

 phpinfo(); ?>

And upload this file to your new server and open in the browser. In the page output find the value for 'register_globals'. If it is off, then you can solve this problem in the following ways

Turn on the register_globals in php.ini by
register_globals = On
(it will not be possible if you are on a shared web server)
Put extract($_REQUEST) on the top of every .php file.
Turn on register_globals using .htaccess make a text file with the name .htaccess and put the following code in it and upload to the root folder
php_flag register_globals on
If you already have a .htaccess file in your website, then simply put this code in it.