Does that mean $ str = str_replace?

[eluser]luisvallin[/eluser]
Does that mean $ str = str_replace in codeigniter
for example

MY_CONSTANT
NEWLINE
SUPER_CLASS_VERSION
$str = str_replace(LD.'foo'.RD, 'bar', $str);

[eluser]Unknown[/eluser]
as i know, that's the function for replacing string which is defined in $str variable

CMIIW, ehe i'm a noob

[eluser]luisvallin[/eluser]
thanks for your opinion