PHP, for long, has been considered as a language for those programmers who cant learn .Net or Java. And the perception got air when people started reading a PHP book for 15 days and start developing websites. About 6 years back, when I started PHP development, it was really different from what it is now.
People used to laugh at some inline PHP scripts within a long HTML page. PHP being interpreted language was also considered to be slow and insecure.
There are lots of good books available for starting to learn the basics of Web Development, in general and PHP, in particular.
One such book, I recommend, is Head first PHP & MySQL. I am a fan of the Head first’s series of innovative books. People may have different opinions on the subject.