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 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%.
Cons
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 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 Poorly designed language, awful syntax & luckily on the decline
Nobody in their right mind is using PHP for new software, if you decide to learn it as your first language you'll be stuck working in teams with old developers who have had no interest in the computer programming field since they landed their first job while maintaining some 2000 era archaic website codebase.