06-02-08, 11:58 AM
If you need to embed dynamic text into static text, you’ll find PHP extremely useful. It was designed for this, and it excels at it. PHP is also very useful for integrating web pages with databases.
The PHP scripting language resembles JavaScript, Java, and Perl, These languages all share a common ancestor, the C programming language. PHP is most different from JavaScript and Java. PHP is a server-side scripting language. All of the “work†is done on the server. JavaScript (and Java) generally run on the client. They have little access to the information that the server has, and mediated access to information on the client. They can do lots of things on the client that PHP cannot. PHP has full access to the information that the server has, and very little access to information that the client has. In fact, it only has information that the client tells the server and that the server passes on to PHP.
Because it is on the server, however, PHP cannot be modified by the client. While you cannot necessarily trust the information that the client gives to PHP, you can trust that your PHP is doing what you told it to do.
Because PHP is on the server end, your PHP scripts can affect your server--such as by keeping an activity log or updating a database.
PHP and Perl often work side-by-side. These are both server-side. Where PHP excels at embedding dynamic content, Perl excels at modifying (or “filteringâ€) streams of text. PHP excels at putting things into documents, and Perl excels at finding things in documents. After you have learned PHP, you may well find Perl useful for many tasks, especially for command-line tasks. PHP has an advantage over Perl on most web sites because PHP is usually loaded as part of the web server. When scripting languages “runâ€, the system has to first load the “interpreter†and then “compile†the language into code that the machine can understand. When you tell PHP to echo the current time to the web page, the computer needs to have your command translated into numbers that it can understand. Because the PHP interpreter is already loaded as part of the web server’s software, it is always running. This cuts out half of that process. The interpreter is already loaded, and it can go directly to compiling the language into code. When web servers see a request to run a Perl script, they usually have to first load the Perl interpreter. This happens very quickly, but when there are thousands or tens of thousands of requests coming every second, every “very quickly†can add up.
C programs are “pre-compiledâ€. They cut out both steps in that process: no interpreter is needed because the program is already compiled into code the machine understands. Because of this, however, C programs must be compiled every time you switch to a new machine. If you move to a different host, you will usually have to recompile your C programs.
Sometimes you’ll even have to recompile your C programs when your ISP upgrades their server’s system software. And many ISPs do not provide you with a C compiler. You’ll find that PHP is more “portable†than C in this respect: if it works on one server, it will usually work on any other server that has it. Most ISPs that provide server-side scripting provide PHP.
The PHP scripting language resembles JavaScript, Java, and Perl, These languages all share a common ancestor, the C programming language. PHP is most different from JavaScript and Java. PHP is a server-side scripting language. All of the “work†is done on the server. JavaScript (and Java) generally run on the client. They have little access to the information that the server has, and mediated access to information on the client. They can do lots of things on the client that PHP cannot. PHP has full access to the information that the server has, and very little access to information that the client has. In fact, it only has information that the client tells the server and that the server passes on to PHP.
Because it is on the server, however, PHP cannot be modified by the client. While you cannot necessarily trust the information that the client gives to PHP, you can trust that your PHP is doing what you told it to do.
Because PHP is on the server end, your PHP scripts can affect your server--such as by keeping an activity log or updating a database.
PHP and Perl often work side-by-side. These are both server-side. Where PHP excels at embedding dynamic content, Perl excels at modifying (or “filteringâ€) streams of text. PHP excels at putting things into documents, and Perl excels at finding things in documents. After you have learned PHP, you may well find Perl useful for many tasks, especially for command-line tasks. PHP has an advantage over Perl on most web sites because PHP is usually loaded as part of the web server. When scripting languages “runâ€, the system has to first load the “interpreter†and then “compile†the language into code that the machine can understand. When you tell PHP to echo the current time to the web page, the computer needs to have your command translated into numbers that it can understand. Because the PHP interpreter is already loaded as part of the web server’s software, it is always running. This cuts out half of that process. The interpreter is already loaded, and it can go directly to compiling the language into code. When web servers see a request to run a Perl script, they usually have to first load the Perl interpreter. This happens very quickly, but when there are thousands or tens of thousands of requests coming every second, every “very quickly†can add up.
C programs are “pre-compiledâ€. They cut out both steps in that process: no interpreter is needed because the program is already compiled into code the machine understands. Because of this, however, C programs must be compiled every time you switch to a new machine. If you move to a different host, you will usually have to recompile your C programs.
Sometimes you’ll even have to recompile your C programs when your ISP upgrades their server’s system software. And many ISPs do not provide you with a C compiler. You’ll find that PHP is more “portable†than C in this respect: if it works on one server, it will usually work on any other server that has it. Most ISPs that provide server-side scripting provide PHP.
Support
Webnetics UK Ltd.
Webnetics UK Ltd.