Now and then you will want to convert your string to lower case. At times when using associative arrays, I prefer to use lower case strings because it’s easier to remember and a good practice to follow the same coding standard, also associative arrays are case sensitive.
The function strtolower() accepts one parameter (string) and returns lower case string on success.
// initialize variable
$text = 'BiG and sMall texT';
// run the variable through the function
$text_lowered = strtolower($text);
// output the result
// Result will be: big and small text
Simple but powerful.