Magic quotes

Magic quotes is a controversial feature of the PHP scripting language, which was introduced to help newcomers write functioning SQL commands without requiring manual escaping. It was later described and widely misinterpreted as help to prevent inexperienced developers from writing code which is vulnerable to SQL injection attacks. This feature is officially deprecated as of PHP 5.3.0, and removed in PHP 5.4 due to security concerns

Safe mode

Safe mode is a diagnostic mode of a computer operating system (OS). It can also refer to a mode of operation by application software. Safe mode is intended to fix most, if not all problems within an operating system. It is also widely used for removing Rogue security software.

The PHP safe mode is an attempt to solve the shared-server security problem. It is architecturally incorrect to try to solve this problem at the PHP level, but since the alternatives at the web server and OS levels aren’t very realistic, many people, especially ISP’s, use safe mode for now.

  • Limit the execution of shell commands
  • Limit access to system environment variables
  • Limit the paths from which PHP can include files using include or require

Simple XML

Simple XML is a variation of XML containing only elements. All attributes are converted into elements. Not having attributes or other xml elements such as the XML declaration / DTDs allows the use of simple and fast parsers. This format is also compatible with mainstream XML parsers.


The PHP Data Objects (PDO) extension defines a lightweight, consistent interface for accessing databases in PHP.


  • Supports 12 different databases
  • Object Mapping
  • Supports prepared statements
  • Supports multiple statements
  • Object oriented interface
  • Named parameters
  • PDO has built-in support for Large Objects (LOBs).
  • When something goes wrong, PDO can throw an instance of its own exception class.
  • PDO does not emulate missing database features.
  • Placeholders within PDO prepared statements need not be named.


Perl Compatible Regular Expressions (PCRE) is a regular expression C library inspired by Perl’s external interface, written by Philip Hazel. PCRE’s syntax is much more powerful and flexible than either of the POSIX regular expression flavors and many classic regular expression libraries. The name is misleading, because PCRE is Perl-compatible only if you consider a subset of PCRE’s settings and a subset of Perl’s regular expression facilities.

The PCRE library is incorporated into a number of prominent open-source programs, such as the Apache HTTP Server and the PHP and R scripting languages; and can be incorporated in proprietary software too (BSD license). As of Perl 5.10, PCRE is also available as a replacement for Perl’s default regular expression engine through the re::engine::PCRE module.


mcrypt is a replacement for the popular UNIX crypt command. crypt was a file encryption tool that used an algorithm very close to the World War II enigma cipher, which was broken. Mcrypt provides the same functionality but uses several modern algorithms such as AES. Libmcrypt, Mcrypt’s companion, is a library of code which contains the actual encryption functions and provides an easy method for use.


iconv is a computer program and a standardized API used to convert between different character encodings.

The iconv API is the standard programming interface for converting character strings from one character encoding to another in Unix-like operating systems. Initially appearing on the HP-UX operating system, it was standardized within XPG4 and is part of the Single UNIX Specification (SUS).



A hash function is any algorithm or subroutine that maps large data sets, called keys, to smaller data sets. For example, a single integer can serve as an index to an array (cf. associative array). The values returned by a hash function are called hash values, hash codes, hash sums, checksums or simply hashes.

Hash functions are mostly used to accelerate table lookup or data comparison tasks such as finding items in a database, detecting duplicated or similar records in a large file, finding similar stretches in DNA sequences, and so on.