There are many languages in which all characters can be expressed by single byte. Multi byte character codes are used to express many characters for many languages. mbstring is developed to handle Japanese characters. However, many mbstring functions are able to handle character encoding other than Japanese.

Depending on your particular setup and personal preferences, there are many ways to access data from your HTML forms. Some examples are

While browscap.ini contains information on many browsers, it relies on user updates to keep the database current. The format of the file is fairly self explanatory.

When a form is submitted to a PHP script, the information from that form is automatically made available to the script. There are many ways to access this information, for example

When using these functions, it is important to remember that while many of them have identical names to their C counterparts, they often have different declarations. Please be sure to read the descriptions to avoid confusion.

PHP scripts often generate dynamic content that must not be cached by the client browser or any proxy caches between the server and the client browser. Many proxies and clients can be forced to disable caching with

The DOM XML extension has been overhauled in PHP 4.3.0 to better comply with the DOM standard. The extension still contains many old functions, but they should no longer be used. In particular, functions that are not object oriented should be avoided.

The query allows to further select certain objects from the list of given objects. Unlike the other query functions, this query may use not indexed attributes. How many object records are returned depends on the query and if access to the object is allowed.

You may also set array cookies by using array notation in the cookie name. This has the effect of setting as many cookies as you have array elements, but when the cookie is received by your script, the values are all placed in an array with the cookie's name

Many web developers are unaware of how SQL queries can be tampered with, and assume that an SQL query is a trusted command. It means that SQL queries are able to circumvent access controls, thereby bypassing standard authentication and authorization checks, and sometimes SQL queries even may allow access to host operating system level commands.

The initial PHP setup and configuration process is controlled by the use of the commandline options of the configure script. This page outlines the usage of the most common options, but there are many others to play with. Check out the Complete list of configure options for an exhaustive rundown. There are several ways to install PHP

The greatest weakness in many PHP programs is not inherent in the language itself, but merely an issue of code not being written with security in mind. For this reason, you should always take the time to consider the implications of a given piece of code, to ascertain the possible damage if an unexpected variable is submitted to it.

You may create different database users for every aspect of your application with very limited rights to database objects. The most required privileges should be granted only, and avoid that the same user can interact with the database in different use cases. This means that if intruders gain access to your database using one of these credentials, they can only effect as many changes as your application can.

The handling of a backslash followed by a digit other than 0 is complicated. Outside a character class, PCRE reads it and any following digits as a decimal number. If the number is less than 10, or if there have been at least that many previous capturing left parentheses in the expression, the entire sequence is taken as a back reference. A description of how this works is given later, following the discussion of parenthesized subpatterns.