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PHP Cookbook by Adam Trachtenberg, David Sklar

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10.1. Using Text-File Databases

Problem

You want a lightweight way to store information between requests.

Solution

Use a text file with advisory locking to prevent conflicts. You can store data in the text file in any useful format (CSV, pipe-delimited, etc.) One convenient way is to put all the data you want to store in one variable (a big associative array) and then store the output of calling serialize( ) on the variable:

$data_file = '/tmp/data';

// open the file for reading and writing
$fh = fopen($data_file,'a+') or die($php_errormsg);
rewind($fh)                  or die($php_errormsg);

// get an exclusive lock on the file 
flock($fh,LOCK_EX)           or die($php_errormsg);

// read in and unserialize the data
$serialized_data = fread($fh,filesize($data_file)) or die($php_errormsg);
$data = unserialize($serialized_data);

/*
 * do whatever you need to with $data ...
 */

// reserialize the data 
$serialized_data = serialize($data);

// clear out the file
rewind($fh)                  or die($php_errormsg);
ftruncate($fp,0)             or die($php_errormsg);

// write the data back to the file and release the lock 
if (-1 == (fwrite($fh,$serialized_data))) { die($php_errormsg); }
fflush($fh)                  or die($php_errormsg);
flock($fh,LOCK_UN)           or die($php_errormsg);
fclose($fh)                  or die($php_errormsg);

Discussion

Storing your data in a text file doesn’t require any additional database software to be installed, but that’s pretty much its only advantage. Its main disadvantages are clumsiness and inefficiency. At the beginning of a request, you’ve got to ...

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