PHP strtolower() Function makes all characters of string to lowercase. It is php in-built function.
string : Required. It is required to make all characters of string to lowercase.
It returns the lowercased string.
Similar function of strtolower():
ucwords(): It makes the first character of each word to uppercase in string.
strtoupper() : It converts a whole string into uppercase.
lcfirst() : It converts only the first character of a string into lowercase.
ucfirst() : It converts only the first character of a string into uppercase.
Let's see below example to understand php strtolower() Function in details.