Perform a MySQL search by relevance in PHP

If you have a database with multiple entries that are similar and you'd like to do a search, you're going to need a way to sort the results. Sorting by the number of times a keyword appears in a block of text is one way, and it's called search relevence. Here is a PHP functions for performing a MySQL database search and ording the results by relevence:

  1. function relevance_search($keyword_raw, $page, $perpage)
  2. {
  3.         $return = NULL;
  4.         $page = ereg_replace("[^0-9]", "", $page);
  5.         $perpage = ereg_replace("[^0-9]", "", $perpage);
  6.         $offset = ' OFFSET '.(($page-1)*$perpage)-1;
  7.         if ($page == 1) {
  8.                 $offset = '';
  9.         }
  10.         $keywords = explode(' ', $keyword_raw);
  11.         if (is_array($keywords)) {
  12.                 $i = 0;
  13.                 foreach($keywords as $value) {
  14.                         $chunk = mysql_real_escape_string($value);
  15.  
  16.                         if ($i > 0) {
  17.                                 $plus = ' + ';
  18.                                 $or = ' OR ';
  19.                         }
  20.                         $keyword_string = $keyword_string.$plus."(CASE WHEN body LIKE '%$chunk%' THEN 1 ELSE 0 END) + (CASE WHEN title LIKE '%$chunk%' THEN 1 ELSE 0 END)";
  21.                         $where_string = $where_string.$or."body LIKE '%$chunk%' OR title LIKE '%$chunk%'";
  22.                         $i++;
  23.                 }
  24.                 $sql = "SELECT *, (".$keyword_string.") AS relevance FROM table_name WHERE (".$where_string.") ORDER BY relevance DESC LIMIT ".$perpage.$offset;
  25.                 $query = mysql_query($sql);
  26.                 if (mysql_num_rows($query)) {
  27.                         $i = 0;
  28.                         while ($row = mysql_fetch_array($query)) {
  29.                                 $return[$i] = $row;
  30.                                 $i++;
  31.                         }
  32.                         mysql_free_result($query);
  33.                 }
  34.         }
  35.         return $return;
  36. }

This function returns all the data matching to inputted keywords, and return an array of results sorted beginning with most relevent (the highest count of keyword matches).

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Compiling an Oracle Instant Client (OCI8) PHP Module

These are the steps involved in creating a PHP module for Oracle Instant Client (OCI8) 1.2.5 (or higher) in Red Hat Enterprise Linux 5.1 or CentOS 5.1. in an x86-64 environment.

Required Packages:

  • gcc
  • glibc
  • httpd
  • libaio
  • make
  • php
  • php-devel
  • php-pear

If you need help installing a package, please read how to install packages using YUM.

32 bit users note: The instructions are exactly the same for a 32 bit OS, just change /client64/ to /client/ in all the commands below.

First things first, go to Oracle:

http://www.oracle.com/technology/software/tech/oci/instantclient/index.html

and download and install the RPM packages for Instant Client Package - Basic and Instant Client Package - SDK. An Oracle Technology Network username/password is required to download the files.

Note: As of writing this, the latest version of the Instant Client package available was 11.1.0.1. If you downloaded a newer (or older) version make sure the use those version numbers in the steps below.

 After downloading the packages, install them using the RPM command:

rpm -Uvh oracle-instantclient-basic-11.1.0.1-1.x86_64.rpm
rpm -Uvh oracle-instantclient-devel-11.1.0.1-1.x86_64.rpm

Once those packages are installed, switch into a temporary directory and enter the following commands to set the required environmental variables:

export LD_LIBRARY_PATH=/usr/lib/oracle/11.1.0.1/client64/
export ORACLE_HOME=/usr/lib/oracle/11.1.0.1/client64/

Also, add those lines to the end of /etc/bashrc so the variables stay effective after reboot.

Note: The following command is only necessary for users installing a version of OCI8 prior to 1.2.5. If you just downloaded the latest version, you can skip this step.

The SDK headers need to be copied into the client library so the compiler can find them:

cp /usr/include/oracle/11.1.0.1/client64/* /usr/lib/oracle/11.1.0.1/client64/lib/

Now comes a challenge that took me a little while to figure out. We want to install the OCI8 package from PEAR, however the package is too large (more than 8 mb) to be handled in memory by the standard PECL installer, so we need to perform an extra step. We're going to use PECL to download the OCI8 package:

pecl -v download oci8

in this case the downloaded file is called  oci8-1.2.5.tgz. Now we use PEAR to install it:

pear -v install oci8-1.2.5.tgz

It should scroll through a bunch of stuff making sure you have the proper software and packages installed on the machine. If everything is in order, it will prompt for the location of the Oracle client libraries. We're going to spcify that it use the Instant Client, and we're going to tell it the location of the libraries with the following line:

instantclient,/usr/lib/oracle/11.1.0.1/client64/lib

When the compilation is complete, you should receive the message "Build process completed successfully". To add the module to PHP, switch into the /etc/php.d/ directory and create a file called oci8.ini, and in it put:

extension=oci8.so

64 bit users installing a version of OCI8 prior to 1.2.5 note:

The module that we just created has to be moved into the 64 bit modules folder

cp /usr/lib/php/modules/oci8.so /usr/lib64/php/modules/

Now all we have to do is restart Apache:

service httpd restart

and take a look at phpinfo() and we should now see a section for OCI8. 

If you're getting an error like:

PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/oci8.so' - /usr/lib/oracle/11.1.0.1/client64/lib/libnnz11.so: cannot restore segment pret after reloc: Permission denied in Unknown on line 0

after compiling and installing an Oracle OCI8 module for PHP you might need to change your SELINUX settings to allow the execution of the oci8.so module or simply disable SELINUX altogether

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Installing Packages Using YUM

These are the step invloved in installing an RPM based package automatically in Red Hat Enterprise Linux 5.1 (CentOS 5.1, etc) using the program YUM.

Required Packages:

  • yum

Most of the entries in this blog have a list of packages at the beginning that are required. Unless otherwise noted, the packages in the lists are all available via YUM (Yellowdog Updater Modified). Please see the documentation that came with your RHEL 5.1 or CentOS 5.1 distribution for installing YUM. Most likely, it's alreay installed on your system.

To install a program using YUM, all you really need to know is the name of the package, and a simple command. For instance, if you wanted to install the package 'httpd' (Apache) you would type:

yum install httpd

If you already have a version of Apache installed, and you want to upgrade it, you would type the command:

yum update httpd

If you want to remove (delete) a package, simply type:

yum remove httpd

For more information, please check out this link:

http://www.centos.org/docs/5/html/yum/

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