A PHP debugger is a software program that evaluates PHP code for syntax and logical errors to enable a PHP scriptwriter to work more efficiently. Many such debuggers exist, and they vary in quality, cost, and complexity. Some function within a complete integrated development environment (IDE) with several sophisticated development tools, while others maintain a single function in a simple interface.
PHP hypertext preprocessor (PHP) is a server-side scripting language that enhances the Web page experience by providing dynamic content to the page in response to user input or other signals. PHP is a recursive acronym, meaning the abbreviation is part of the name. The first letter, P, stands for PHP in the abbreviation.
Server-side software resides on the server, the computer hosting the Web page, and handles data manipulation and storage on the server as opposed to the user side, called the client side. It is a scripting language in that PHP is not a fully developed language with a compiler to create executable files, but rather adds segments of code into the web page source code. The Web page source code is written in hypertext markup language (HTML). PHP code may be thought of as a specialized HTML code. For that reason, a PHP debugger has to include an HTML debugger as well.
PHP is popular because it is easy to learn and it interfaces with structured query language (SQL) databases and with Apache, a common server software, and is readily available without charge to any developer. Because PHP is so accessible, new programmers use the language and help drive the market for a PHP debugger. Many of these programmers are familiar with what-you-see-is-what-you-get (WYSIWYG) Web development tools such as Microsoft FrontPage® and desire the same ease of use while developing PHP applications.
Features that a PHP debugger might display include step-by-step execution, watchpoints, and redo/undo. A debugger might keep a history of changes and let the user pick up execution where desired. A stack trace function allows the developer to see the lines that were executed and the value of variables before an error. A program’s ability to recognize syntax errors, which are often typing errors or simple command misuses, is a key to its usefulness. An intelligent debugger will anticipate what the syntax should be and either correct the error automatically or suggest the correction to the user.
In a full IDE PHP debugger, portions of the display will be devoted to a real-time output from the running Web page. Multiple scripts may be able to run simultaneously. The ability to switch the code between development test computers and the Internet servers without code modification is very useful. A PHP profiler may be included with a PHP debugger. This software tracks metrics of the Web page, such as how many queries are open or how long it takes for the program to execute.