PHP function start with “function function-name()”.PHP Function name must be start with character and it accept alphanumeric and _.
In build functions are case in-sensitive.
User build functions are case sensitive.
We can pass upto 64 parameter as argument.
Anonymous function are user defined function which have “no-name” and also called closures.
PHP support variable functions. Means when you can call a function using variable.
In same file OR under same class, same function name can’t be created.