From MySQL to PostgreSQL

Hi. I developed a forum using php5 and mysql. Right now I'm hosting it on my computer, for version for myself and another for a school I volunteer at. I would like to move the forums to the school's server. Apperently they don't have MySQL, they have PostgreSQL. I was just wondering, how much like MySQL is PostgreSQL? Would it be possible to create general functions (MySQL style) that could also work for PostgreSQL, based on what a config file set? Right now I have a file that's specific to each forum, so I could specify PostgreSQL or MySQL and based on that the function would do the appropriate action. So how much like MySQL is PostgreSQL? -- Marcjon