Recs.
Updated
PHP is a server-side scripting language that is most often used for web development. However it is also used as a general-purpose programming language.
SpecsUpdate
Pros
Pro Widely used for websites
PHP is the quasi-standard for backends for web applications and used by most of all websites. Many popular CMS are built with PHP, e.g. Wordpress, Drupal and Joomla.
Pro Tight and easy integration with HTML
Unlike some languages, PHP is designed to work as part of an HTML file, and moving in and out of straight HTML and PHP is simple and seamless. If you're familiar with HTML, adding simple PHP gives you access to creating dynamic pages and sessions very easy. You have easy and logical access to headers, session variables, cookies, GET and PUT information and files.
Pro One of the most common languages
According to the 2015 Stack Overflow Developer Survey (26,086 people surveyed), PHP was the 5th most popular/used language at 29.7%.
Pro Tons of built in functionality that don't require external libraries like most other languages
Cons
Con Very slow compared to alternatives
Compared to alternatives like Exilir and Go-lang, which provide comparable functionality, even the latest versions of PHP are vastly slower than their competitors. The difference is so significant that it has the potential to bottleneck even modestly sized applications and lead to highly significant increases in hardware costs, even with well-written code. PHP's syntax is also highly permissive of non-optimized code which can further exacerbate this issue.
Con A big patchwork
Each new version adds a patch to this improvised language. It always gets better, but you can still see the patches everywhere.
Con Poorly designed language
Despite its widespread use, PHP is generally looked upon poorly from a design point of view. The consistency of function names and function argument order, lazily and borderline non-functional implementation of object oriented programming, can only receive requests via POST methods, slow version adoption (the PHP you learn right now may not work on every webserver you'll work on), and a focus on "hacking things together" rather than "doing it right". These are all very common complaints when it comes to working with PHP. While not a bad language to learn, PHP is not at all a good language to learn first, as it will probably teach bad habits.
Con Often awkward setup
PHP setup can be awkward and differ significantly on different platforms in ways that are not always entirely justifiable. Often old versions of PHP (5.6) will conflict with newer versions (7.x) when working with legacy installations, and configuration of php-fpm when working with nginx can be overly complex for first-time setup, particularly for small to mid scale projects. Because the language has grown as a patchwork, different PHP documentation often provides conflicting and out of date info, which can cause system-wide problems if implimented by someone of junior or even intermediate skill. While this is also true of other languages, it is especially so of PHP, and significant development time is often lost on issues that sensible defaults would fix. While the Laravel framework, particularly in concert with Homestead, does mitigate these issues, it is by no means a universal panacea, as it will not be possible to impliment in many real-world situations.
Con Immense catalog of insecure frameworks
The most serious security problems in websites on the web today are almost universally found in popular PHP frameworks, CMS platforms, libraries and code samples, almost all stemming from poor language design, bad tutorials and awful resources.
Con Ugly syntax
The naming of string and numerical functions is awkward, frequently inconsistent and impossible to memorize - you will always need a handy cheat sheet.
Recommendations
Comments
Out of Date Pros + Cons
Con Lacks many features
There are far more superior languages than php in terms of productivity , both dynamically typed(e.g. Ruby , Python) and statically typed(not necessarily C# but kotlin, Scala, etc).