The dollar sign makes a variable. Variables can be numbers or letters, PHP will do whatever you want with them.
$mytext = 'Hello World!';
Use a period to smush strings together.
$mytext = 'Hello World!'.'<br> How are you today?';
How are you today?
Unix languages handle dates in a wonderful way... in datestamps that measure the number of seconds since the epoch. Let's say I was born April 14th 1980 and want to know how old I am:
$rightNow = time();
$myBirthday = mktime(5,7,1,4,14,1980);
$myAgeInSeconds = $rightnow - $mybirthday;
// Tranlate this to days,
// easy since there are always 60 seconds in a minute,
// 60 minutes in an hour, 24 hours in a day.
$myAgeInDays = $myAgeInSeconds/(60*60*24);
Performs regular expressions. These are huge and powerful and can be complicated. I'm just adding this bit of code I use all the time. It filters out non-alphanumeric text and is very handy
for making sure bad people aren't doing sneaky security-risk type things with your forms.