Heating methyl phenyl ether with HI gives

$\mathrm{Ph}-\mathrm{O}-{\mathrm{CH}}_3\stackrel{\mathrm{HI}}{\to }\mathrm{Ph}OH +{\mathrm{CH}}_3\mathrm{I}$

or

The carbon-Oxygen  bonds of phenols are strong due to partial double bond nature, being much stronger C-O of alcoholic breaks.