As others have pointed out, your original suggestion will not work. You could use PWM output and a filter which may work (you will need quite a large capacitor and/or resistor. The input at the other end would only be an approximation of the output (you could calculate based on detailed knowledge of component values and frequencies). Depending on the rate at which the value changes you may get different values on each read.

There are better ways. As suggested, serial will work (either hardware or software depending on other factors), and is probably easiest. You could use any of the common communication protocols (I²C or SPI) or even send values via IP.

As others have pointed out, your original suggestion will not work. 

You could use PWM output and a filter which may work (you will need quite a large capacitor and/or resistor). The input at the other end would only be an approximation of the output (you could calculate based on detailed knowledge of component values and frequencies). Depending on the rate at which the value changes you may get different values on each read.

There are better ways. As suggested, serial will work (either hardware or software depending on other factors), and is probably easiest. You could use any of the common communication protocols (I²C or SPI) or even send values via IP.