PHP For PERL Developers

PERL is a dynamically typed, high level and general-purpose programming language. It is normally believed that PERL is an acronym for Practical Extraction and Reporting Language. PHP on the other hand is also a general-purpose scripting language. Initially PHP used to be a short for Personal Home Page’, but these days it has now been recognized as a recursive acronym ‘PHP: Hypertext Preprocessor’.

In this chapter, certain major similarities and differences in between PHP and PERL are listed. This will help PERL developers to understand PHP very quickly and avoid common mistakes.

Similarities between PERL and PHP

Both Perl and PHP are scripting languages. They are not used to build native standalone executables in advance of execution.

Early versions of PHP were inspired by PERL. PHP's basic syntax is very similar to PERL. Both share a lot of syntactic features with C. Their code is insensitive to whitespace, Each statement is terminated by semicolons.

Both PHP and PERL use curly braces to organize multiple statements into a single block. Function calls start with the name of the function, followed by the actual arguments enclosed in parentheses and separated by commas, in both the cases.

• All variables in PHP look like scalar variables in PERL: a name with a dollar sign ($) in front of it.

• Since both the languages are dynamically typed, you don’t need to declare the type of a PHP as well as a PERL variable before using it.

• In PHP, as in PERL, variables have no intrinsic type other than the value they currently hold. You can store either number or string in same type of variable.

• Both PHP and Perl do more interpretation of double-quoted strings ("string") than of single-quoted strings ('string').

Differences between PERL and PHP

PHP can be embedded inside HTML. Although it is possible to run a PHP script from the command line, it is more popularly used as a server-side scripting language on a Web server and used for producing Web pages.

If you are used to writing CGI scripts in PERL, the main difference in PHP is that you no longer need to explicitly print large blocks of static HTML using print or heredoc statements and instead can simply write the HTML itself outside of the PHP code block.

No @ or % variables − PHP has one only kind of variable, which starts with a dollar sign ($). Any of the datatypes in the language can be stored in such variables, whether scalar or compound. In PERL, the array variable is prefixed with @ symbol. Also, the hash variable is prefixed by % symbol.

Unlike PERL, PHP has a single datatype called an array which can be an indexed array or associative array, which is similar to hash in PERL.

Function calls in PHP look pretty much like subroutine calls in PERL. Function definitions in PHP, on the other hand, typically require some kind of list of formal arguments as in C or Java which is not the case in PERL.

Scope of variables in PERL is global by default. This means that top-level variables are visible inside subroutines. Often, this leads to promiscuous use of globals across functions. In PHP, the scope of variables within function definitions is local by default.

No module system in PHP as such. In PHP there is no real distinction between normal code files and code files used as imported libraries.

Break and continue rather than next and last − PHP is more like C language and uses break and continue instead of next and last statement as in PERL.

No elsif − A minor spelling difference: Perl's elsif is PHP's elseif.

In addition to Perl-style (#) single-line comments, PHP offers C-style multiline comments (/* comment */) and Java-style single-line comments (// comment).

Regular expressions − PHP does not have a built-in syntax specific to regular expressions, but has most of the same functionality in its "Perl-compatible" regular expression functions.