Introduction to Built-In Functions

PHP comes with many built-in functions, such as strtoupper, which changes the case of an input string to uppercase:

echo strtoupper('Foo');
// output: FOO

PHP natively comes with a ton of functions. By adding extensions to PHP, you add even more built-in functions and classes to it. Built-in functions are precompiled in C as this is the language that PHP and its extensions are written in.

Note

How to add an extension will differ depending on which operating system you are on. So, when searching for it, always add the name of your operating system to your search and be sure to consult the most recent results first, as they are more likely to outline the correct procedure for installing or compiling extensions into PHP.

There is hardly anything more frustrating than spending days on writing some functionality, only to discover toward the end that there is a built-in function that does the same thing five times faster. So, before...