PHP is another computer language. In a way, Perl and PHP are competitors in the programming world. Both languages have relatively similar learning curves, work well in the server environment, and have similar overall capabilities.
As you would expect, each language has its pros and cons. Ideally the webmaster would be able to use either language and choose the best one for a given project. However most programmers have a preference for one over the other and will tend to use their favourite.
In recent years PHP has become more popular with new programmers, in particular, web designers learning their first programming language. This may be because PHP is slightly easier to learn from a web design point of view. PHP pages are constructed like HTML pages, with standard HTML markup. PHP code is inserted into the page and executed when the page is requested. Conversely, Perl scripts are run as stand-alone programs and create HTML pages when the script is run.
Another issue is speed and efficiency. PHP is generally considered to be faster than Perl, although this is debatable. In any case there are certainly ways to make Perl perform as fast. PHP supporters often cite speed as a good reason to choose PHP, but in reality it is not normally a concern and any differences are usually academic.
Perl is a very powerful, robust language with more history than PHP. Although the newbie might think that Perl is more complicated than it needs to be for web development, experienced programmers will appreciate the vast array of options available with Perl.