How to implode newlines/break lines to a space?

How to implode newlines/break lines to a space?

given these $strings:

The quick brown
fox jumps 
over the lazy
dog

imploding those strings with a blank space

$keys = implode(' ', array_keys($strings));

I have this:

The quick brownfox jumpsover the lazydog

And I'm trying to have this:

The quick brown fox jumps over the lazy dog

Any lights? Thank you.