MySQL – Inserting and reading BLOB’s in PHP


This paper provides the code needed to both write binary content to a MySQL table and to read the same data back. In our example, we will create two scripts, one that reads the contents of a PDF file and adds this into a table. The second script will read the contents of the same record in MySQL and output it to a file. We will then show that the two files are identical.

The table that we created is as follows:

CREATE TABLE testblob(
  id INT AUTO_INCREMENT ,
  data MEDIUMBLOB,
  PRIMARY KEY ( id )
) ENGINE = InnoDB;

The first script reads the contents of a PDF file called itiss.pdf.

<?php
	$dbh = mysql_connect("localhost", "user");
	mysql_select_db("test");
	$data = file_get_contents("itiss.pdf");
	// This is important to avoid a ' to accidentally close a string
	$data = mysql_real_escape_string($data);
	mysql_query("INSERT INTO testblob(data) VALUES ('$data')");
?>



At this point the binary has been added into the database. We now need a second script which will read this content and write it back out to a separate file:

<?php
	if(!$dbh = mysql_connect("localhost", "user")) {
		die("ERROR: " . mysql_error());
	}
	mysql_select_db("test");
	if(!$res = mysql_query("SELECT data FROM testblob WHERE id = 1", $dbh)) {
		die("ERROR: " . mysql_error());
	}
	$row = mysql_fetch_assoc($res);
	$data = $row['data'];
	file_put_contents("itiss1.pdf", $data);
?>

To see this in action:

$ mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 64
Server version: 5.0.45 SUSE MySQL RPM

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select count(1) from testblob;
+----------+
| count(1) |
+----------+
|        0 | 
+----------+
1 row in set (0.00 sec)

mysql> quit
Bye
$ php writeblob.php 


$ php readblob.php 


$ ls -ltr
total 52
-rw-r--r-- 1 rcashell users   108 2011-01-10 09:40 blob.sql
-rw-r--r-- 1 rcashell users 17453 2011-01-10 10:00 itiss.pdf
-rw-r--r-- 1 rcashell users   298 2011-01-10 10:06 writeblob.php
-rw-r--r-- 1 rcashell users   366 2011-01-10 10:06 readblob.php
-rw-r--r-- 1 rcashell users 17453 2011-01-10 10:15 itiss1.pdf


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