Rasmus Lerdorf, the father of the PHP language, explains the $ sign as an
ability to insert variables inside literal string values (interpolation), so
that the variables are distinguished from the rest of the string. A dollar sign
in front of variables in PHP is inspired by Perl which greatly influenced PHP
during its early years.
Many other programming languages also use a dollar sign in their syntax. This symbol is called “sigil” and simplifies interpolation.
Names not prefixed by $ are considered constants, functions, class names, etc.
Sigil usage simplifies the variable interpolation into strings:
<?php
$name = "World";
echo "Hello, $name";
Where as in languages without sigil usage (for example, Python), you must either concatenate strings:
# Python
name = "World"
print "Hello, " + name
or use special interpolation syntax if the language provides it. For example, Ruby:
# Ruby
name = "World"
puts "Hello #{name}"
Many people used to other languages might find the sigil usage odd, but you can get used to it in no time and discover its benefits.
